Skip to content Skip to side menu

Performance Racing Technology




By Jean Genibrel, 

Around the end of the year, our race or performance cars and tow vehicles are often stowed away and sometimes forgotten until spring. Storing vehicles can create problems unseen during normal operation. Vintage and race cars, weekend time trial or drag cars, Jeeps, Off-Road vehicles, Street Rods, street performance cars, and tow vehicles, when stored in the winter, require some attention to prevent big problems in the spring. 

The Cooling System:

Racing organizations forbid the use of antifreeze due to its slipperiness, but street-driven vehicles should have the antifreeze checked to prevent cracking the engine and the radiator in freezing temperatures. Even a small amount of water can crack a radiator when the water freezes. If the car is to be stored, drain the water completely from the engine and the radiator. The picture below shows the kind of damage a freeze can do to a race motor that contains only water.

 This picture from Maropulos Racing Engines clearly depicts the type of problem that can be avoided by winterizing your race car.




Jean Genibrel, the owner of, manufactured Checker Racing Batteries in the late 1980s. The batteries were gel-type, deep cycle, with thick plates and all the necessary accouterments to make them fit for racing. Nevertheless, in the spring, we would get calls from racers and street rodders who had “dead batteries.” This problem was due to poor preparation for storage.

Unfortunately, the new AGM batteries are most susceptible to going dead when left unattended for some time, especially if they were stored when partly discharged. This problem is due to their thin plate construction. Some precautions can alleviate battery problems.

Modern automobiles and trucks support multiple electrical devices like clocks, radio presets and security systems that can discharge a battery in less than a month when the car is unused. Connect a battery maintenance device for the storage duration will ensure the battery will be operational in the spring.

Owners of race cars without an alternator should fully charge their battery and connect a maintenance charger before storage.

Battery Tender trickle charger

Battery Tender company products are available on For storage buy a trickle charger, not a full bore charger or one of those will overheat and destroy a battery over a period of time.

Oil Thermostats:

Engine builders recommend using an oil thermostat when using a vehicle equipped with an oil cooler in the winter. In some parts of the U.S., like the low lying areas of California, will never see freezing temperatures. However, driving a few miles into the desert- where we can find many race tracks -  or in the mountains, the temperature can drop dramatically and quickly. Cars like Vintage ones, weekend time trial cars, and street performance cars driven in the winter and equipped with an oil cooler would benefit from and oil thermostat. Motor oil, unlike automatic transmission fluid, must warm to at least 165 degrees F. High oil pressure may sound like a good thing, but when very cold, oil does not flow, and this can cause severe engine damage. 


If you will drive your car during the winter, refer to the owners’ manual to determine which viscosity oil to run in your engine during those months. Even low viscosity oil can get very thick at low temperatures. Tow vehicles are also candidates for an oil thermostat when they are equipped with an oil cooler.

During storage, motor oil may gather some water, so change the oil after storage.


Used racing tires will be unusable by springtime anyhow so you could leave them on the wheels for now. Tire Rack offers the following information for storing high performance and racing tires: It is not recommended to drive on these types of tires at temperatures below 40 degrees F (5 degrees C). It is recommended these types of tires be stored indoors at temperatures maintained at above 20 degrees F (-7 degrees C) when not in use.

Automatic Transmissions:

Automatic transmissions can fail if they are left to stand for long periods. When left undriven, varnish and acids form in the fluid, causing the seals to dry and crack. So perhaps once a month or so, start the engine and drive the car for a few miles (if possible) or go through the gears on the jack stands.


Sunoco Race Fuels suggests the following as guidelines for "optimizing the “shelf life” of racing gasoline but does not cover safety aspects of handling gasoline."


  • Keep the fuel in tightly sealed steel containers to prevent evaporation of some of the more volatile components of race gas.
  • Fill gas tanks and drain the old fuel from the injection system or carburetors.
  • Cover open fuel lines and breathers with plastic baggies and tie-straps.
  • Keep fuel in areas with low-temperature swings.
  • Add some Sta-Bil fuel stabilizer to the fuel if you plan to store it for more than a year.


  • Critters, even house pets, can find refuge in the strangest places. One of our correspondents had stored his Crossfire in the fall, and in the spring, when he started the air conditioning, he noticed a nasty smell accompanied by a huge vibration. Upon disassembling the AC, he found a mouse that had seen better days in the cage fan. Further investigation revealed the little guy’s family and friends also had a voracious appetite for wires and upholstery. Adding some shields around the jack stands may discourage rodents from climbing into chew heaven.


  • Car museums wrap their cars when they go into storage with stretch plastic wrap — lots of work, but worthwhile protection.
  • A few bags of desiccant from your local hardware store placed on the floor and in the trunk will help remove moisture from the interior.
  • Check for fluid leaks. Over a long winter, fluids can make a real mess of a shop floor, and they can ruin tires that are still on the ground.
  • Adding a bottle of Sta-Bil fuel stabilizer to a full tank of gas will keep the fuel fresh for several months. Fill the tank and run the engine for a few minutes to use up the fuel in the lines and the filter. The full tank will reduce the air and moisture gap above the fuel.
  • Keep cars stored in a dry place away from leaky roofs or floods.
  • Store your vehicles away from sandblasters, welders, grinders, and other shop equipment.
  • Cover the vehicle with a waterproof tarp or dedicated car cover, but heed the advice of using desiccant as the covers may retain moisture.
  • Place barriers around the car like cones or barrels to keep other cars at a safe distance.
  • Wrap carburetors in plastic bags to prevent moisture from entering the engine. The same goes for the exhaust.

Happy Performance Motoring

Jean Genibrel

Read more →



...clutch stall speed adjustment is achieved by turning the screws holding the springs in place. Most clutches include four to six springs and adjustment screws... Clutch Stall RPM Race Settings: Briggs Animal 4,000-4,500...Practice Day: Tuning the carburetor, reading the plug, flags, checklists...Race Driving basics...Race Day Setup...Racing...Passing...Carburetors...Exhaust flex...Spark Plugs...Shifters...

Read more →




A Book by Multiple Award Winning Author Jean Genibrel

 For the Expecting Karter and Novice


Make your karting experience rewarding and long lasting.


Nothing is "secret" in racing. There are only some things you do not know and need to learn. This could take years. "Karting a Complete Introduction" details all the information a prospective or new karter needs to know to start in go kart racing.



Be ready for your first event with all the knowledge and equipment you need. Read 'Karting a Complete Introduction' and get a whole season jump on the competition.











Jean Genibrel is the only karting author to have been awarded for his karting magazine articles and books. Jean is a member of the American Automobile Racing Writers and Broadcasters Association who awarded the author in the historical category for a magazine article and for the book "Karting a Complete Introduction".

Jean Genibrel, the most read karting book author in the world, has been involved in karting for nearly four decades and he has written eight books and a multitude of magazine articles. Jean was involved in all categories of karting; four-stroke, two-stroke, Shifter, dirt oval and Sprint. General has written seven books on a variety of subjects like karting, stock car racing, road racing and open-wheel dirt cars. Jean was the editor for 'Kart Racer Magazine' and several other publications. He has contributed to several other race-oriented books and magazine articles. With nearly 80,000 books sold, Jean has helped thousands of karters become acquainted with the sport of go-karting. As a race professional the author has gained firsthand experience with the mistakes and errors many have made trying to enter karting. "Karting! a Complete Introduction" takes the novice karter through the daunting terminology of karting, leading him toward making comfortable purchases appropriate to the form of karting he plans to enter. The author publishes 'KARTING A Complete Introduction', 'Sprint Karting', 'The Yamaha KT100' and 'APPLIEDSPEED.COM a technical auto racing blog and E-commerce website.



Many new karters show up at their first event, be it a karting practice or kart race, and they find they have purchased the wrong equipment, they are missing a tool or they have the incorrect tires for the track or the club’s specs. Buy 'Karting A Complete Introduction' and get all the answers to the questions you do not know you should be asking.



Honda offers two and four stroke engines for karting. Know which one you want for your chassis. Briggs and Stratton also offer the World Formula that is a four-stroke and Rotax has a nice two-stroke program too. 







HOW DO I GET INTO KARTING?  Chapters include all the answers a novice or prospective Karter could have: What kind of equipment do I need? The book includes a complete list of all the parts, spares, tools, etc that you will need for your first outing.

WHERE can I race my go-kart? The book includes a list of tracks and Internet links for where to go kart racing legally and safely.

Go kart racing has classes for all ages, speeds, types of engines and abilities. 'Karting a Complete Introduction' offers all the information you will need to go kart racing.




With WHOM should I race my go-kart? Clubs all over the US and CANADA hold weekly events in Sprint, Dirt Oval, and Paved Oval track karting. Others are into Vintage Karting and some like Road Racing. Keep in mind that each one of those forms of karting requires its own equipment and tires. The book helps you choose a class to fit your budget, your age, experience, and aspirations.

Most, if not all, professional race car drivers have started in karting. Karting has classes for drivers as young as 8 years old.Tony Kart has been a major supporter of professional karters. Perhaps you too someday will have a trophy case like this one.


WHAT kinds of engines are used in karting? The most common four-strokes include Briggs & Stratton and Honda go-kart engines. The two strokes (often called two-cycles) include primarily the Yamaha KT100 with a clutch and a “Can” for exhaust and the Rotax. The Shifter engines include primarily the Honda five-speed. There is also the “TAG” classes and engines that again require specific engines and clutch types. Again, you do not want to show up at a Sprint race with an Oval track chassis and engine or arrive at an oval race with a Shifter Kart. 


WHY do you want to race go karts? Answering this question and others will place the rest of the equation in perspective. Reading the book will set you on the path to success by being prepared and ready with all the stuff you need to go karting.

"Dirt Track" racing is also called "Speedway", "Dirt Oval" or just "Circle Track". Check with your local track or kart shop where this form of karting is practiced. Some parts of the US and Canada only offer Sprint, while others primarily have Oval racing. Each form of karting demands its own chassis, engines, tires and safety equipment. Know what to get before you decide to go racing...Buy "KARTING a COMPLETE INTRODUCTION'" 





Make sure to get the right equipment. Despite all the efforts by organizers, associations and manufacturers kart racing still retains an element of danger. Read 'KARTING a COMPLETE INTRODUCTION' and get the right equipment from a reputable manufacturer.





You will need some basic tools. Learn which ones so you will not be caught short when you get to the track.

























  • Parts from the kart shop
  • Choosing an engine                                                
  • Choosing a chassis
  • Tips on choosing a helmet
  • Points to consider
  • Engines, divisions, classes
  • Karting basics
  • Dirt, Sprint, Road Race, Vintage
  • Two and Four Strokes
  • Engines, Chassis, clutches
  • Buying used or new?
  • European and domestic chassis
  • Dealing with a kart shop
  • Schools, tracks, and associations
  • Lists of tools and spares
  • Buying the right equipment
  • Questions most often asked
  • …and everything else a prospective kart racer NEEDS to know!

A new shining and a colorful helmet is neat but remember that proper fit, comfort, and safety are primordial in karting.


I recall three young gentlemen at Ascot Park in Gardena, California, who seemed to be struggling with their setup. This was when my first book on karting came out in 1984. The trio bought one of the books and the next race their lap times dropped dramatically. Tony Pedregon came to me and said: 'We did not even know what stagger was'.”


 My karting and racing experience spans nearly four decades. As a professional journalist, racer, and author I have remained focused on the procedures a new karter must go through to ease his way into the sport. Using the information in my books will take a new karter from the first buy at the kart shop, or on the internet, to the front row in a fraction of the time others have taken. In 'KARTING! A Complete Introduction' I offer never before available information for the prospective Karter in a well-paced learning curve. The book is the singular source for karting information to guide the new or prospective kart racer through all the buying decisions and to get him to his first race ready to go. From choosing the karting class, the division, the kart chassis and go kart engine type, to finding the correct safety equipment such as karting gloves, suits, and helmets, it is all there




'THE YAMAHA KT100': Racing, blueprinting, tuning, machining, cooling, lubrication, making more power, carburetor flowing, port settings and a lot more info never before divulged. Do not get left behind. Many drivers have gone from the middle of the pack to the front just from learning how to tune the carburetor and the clutch. $24.95 GET FREE PISTON LOCATION vs PIN OFFSET XL CALCULATOR WITH PURCHASE OF 'THE YAMAHA KT100'       'KARTING SPRINT', oval and dirt: Covers Sprint and Oval track kart racing. Engines, tuning, settings, driving, chassis setups, and most importantly how to go faster. $21.95


APPLIEDSPEED, Jean Genibrel, is, (are)  a member (s) of, or is (are)certified by, the following organizations:                SEMA/PRI, ASE, AARWBA, SME, MPG


Read more →




jeff gordon tape on grill

Adding tape to the front of the grill helps race cars turn, accelerate and brake more effectively. In turn, the reduced cooling must be overtaken by the cooling system. The new racing radiators can handle extremely high pressures and temperatures.


New radiators, especially those of the double pass design, have been designed to increase the internal pressure of race car cooling systems. Companies like C&R Racing and Griffin Radiators have been involved in racing throughout the world with some of the best race teams in all forms of racing. There, the companies learned the importance of the pressure that is present in the cooling system to aid in gathering heat (calories) from the engine, particularly the cylinder heads above the combustion chambers.




Radiators come in a multitude of dimensions, quantity of rows and configurations such as double or single pass, thickness, and location of the filler neck if one is used on the radiator.

 cross flow and downflow radiators

A radiator with its core running vertically is called a downflow radiator. This design is the most ubiquitous among OEM and racing radiators. In this type of radiator, the water runs from top to bottom of the cooler. A radiator with tubes running horizontally is known as a crossflow radiator. As the name indicates, the water flows horizontally from one side of the radiator to the other. Neither of those designs proves to hold a distinct advantage over the other. However, a particular design may be more convenient than the other. The crossflow design can allow the radiator cap to be positioned on the low-pressure (suction) side of the system, which prevents the pressure created by a high-flow water pump from forcing coolant past the radiator cap at high rpm.



Coolant recovery tankOpen radiators with a cap need a recovery tank to receive the excess coolant that has passed through the cap. The radiator first expels the air at the top of the radiator and then, when the water cools, the negative pressure in the radiator aspirates some water to fill the void the air had occupied above the radiator.



AFCO aluminum recovery tank

Closed radiators require a pressurized recovery tank that includes a filler cap.  Recovery tanks allow for easy and fast burping of the radiator. These tanks must be installed above the highest point of the cooling system.The outlet of the bleed must connect to a surge tank.


Radiator Styles

Three styles of radiators are available to racers:

  1. Open radiators with a cap and a recovery tank.
  2. Closed radiators with a surge can and recovery tank.
  3. Pressurized systems that do not include a cap but instead they utilize an accumulator with an air spring and a PRV.
AFCO tall racing coolant recovery tank

Recovery tanks should be as tall as possible to allow all the air in the water to rise to the top of the tank. These tanks recover the hot water that was expelled from the radiator when the water heated up. To ensure that no air will re-enter the cooling system when the water recycles back to the radiator, the manufacturers install the return hose fitting at the bottom of the tank.


The major factors to consider when choosing a racing radiator must include: 

  1. The form of racing: Circle Track, Road Racing, Drag Racing, Off-Road etc.
  2. What is the average speed that the car will attain?
  3. What is the average RPM the engine will turn and for how long?
  4. What is the possibility of the radiator becoming damaged or plugged with dirt and rocks, and tire rubber?
  5. Will the vehicle be in go-and-stop traffic like in Drag Racing or with a dual purpose street-and-race vehicle?

In any of the above situations using something purpose-built resonates. OEM is for OEM cars. Race parts are made for racing.

Truck off road radiatorThis photo depicts the importance of including the radiator in the race vehicle design. Here, the builder fitted a wide radiator to lodge above the bumper for protection and to fit under the hood. The width and height of a radiator do not matter, whereas the thickness and surface area are crucial to proper cooling. Off road racing cars and trucks require purpose-built racing radiators to sustain the rigors of vibrations, rocks and mud.



How do double pass radiators work?

What makes a double pass radiator more efficient?

Many racers and gearheads believe that a double-pass radiator improves cooling performance. This impression emerged from the erroneous notion that passing the coolant twice through the radiator will make the coolant remain in the radiator twice as long, thus improving the cooling performance. In a double pass radiator, however, only half of the coolant passes through the radiator at one time. Twice the time at half the volume takes us back to the same place as with a single pass radiator. So what is the point of a double pass radiator?Drawing of double pass radiator                                                             

A double pass radiator has the intake and outlet on the same side. Installing a baffle in the tank that separates the inlet and the outlet prevents the water from flowing straight through from the inlet to the outlet. Passing the coolant twice through the radiator does not cool better than a single pass because only half the coolant volume passes through.

Cooling Benefits from Double Pass Radiators

Passing the coolant through one-half of the radiator twice doubles the coolant speed and its pressure.  However, since a double pass radiator reduces the volume of water that passes through the core in half, its pressure also doubles. The increase in pressure in the cooling system is where the cooling benefits emerge. In the heads principally, the pressure reduces small air pockets and it reduces the onset of nucleate boiling and preignition. What is more, the pressure forces the coolant deeper into the recesses that the casting process left behind where it can absorb additional calories.

Advantage of Installation of a Double Pass Radiator

One of the reasons double pass radiators are used is that on some vehicles the inlet and outlet need to be on the same side of the radiator to accommodate the plumbing. Placing the inlet and outlet on the same side of the radiator on a single pass radiator would cause the water to stop flowing through the tubes as the water would enter and exit the same side of the radiator. To avoid this situation, manufacturers insert a baffle between the top and lower portions of the radiator. In this case, the coolant flows in one direction, and it returns in the other. Half the water passes twice through the radiator at a time. 



Running the highest pressure the system can handle is the best method of preventing overheating and detonation.  High-pressure systems reduce hot spots, steam pockets and they increase the boiling point of the water compared to lower pressure systems, while they allow using smaller grill openings to help aerodynamics and downforce.  Radiator caps are rated as high as 30 psi. These caps can only be used with quality brazed radiators vs. the OEM ones that are sealed with epoxy.


radiator cap cutaway

These drawings show how radiator caps work in releasing the pressure, and how they allow the water to return to the radiator when it cools down. racing radiator cap

Generally, 25-psi is the maximum pressure quality radiator caps are rated for.  A high-pressure radiator cap, like those produced by AFCO Racing, is well advised with race cooling systems that do not use a thermostat or restrictor. There, if the cap is installed on top of the radiator, the pressure created by the water pump can lift the pressure valve of the cap and create a condition that can easily be mistaken for a blown head gasket.

It is a good idea to check the cap periodically to ensure it is sealing correctly and the rubber seal has not lost its elasticity.  The filler neck’s sealing surfaces must be free of defects, or the closed system could lose water (and pressure) slowly and cause an overheating issue.  This can cause a condition that appears to be a blown head gasket when it is due to pressure loss and the fluid boiling. This will eventually cause the head gasket to blow. So what came first the blown head gasket or the overheating?


Water pressure gauge auto meter appliedspeed.comAuto Meter warning light

A blown hose down the straight away will send you into the wall in a hurry. A water pressure gauge with a light will let you know if you should back off for the next turn. If the system has lost the majority of its water the temp gauge will not read hot but the pressure one will show low pressure.  A typical case of "Trust, but verify".


Radiator caps come in several configurations. Aim for a higher pressure cap for race applications and heavy duty towing, off-roading and heavy equipment. If you need more than 25-lbs go with a pressurized cooling system from Applied and C&R Racing. Inspecting the rubber pressure seal on race radiator caps should be a part of the in-between race maintenance schedule.

C&R High Pressure System

High-pressure systems produced by C&R Racing do not use a pressure type of radiator cap. Instead, the systems are equipped with an adjustable pressure relief valve. These systems can hold up to 60 to 70 PSI of pressure.


Evans drawing of nucleate boiling

This drawing from Evans Waterless Engine Coolant identifies the areas most prone to boiling in the heads. These spots reside above the combustion chamber and the exhaust port. Once the water reaches Critical Heat Flux, the steam creates a barrier between the metal and the coolant. This condition can lead to pre-ignition, detonation, pinging and severe engine damage. 



The secret of the thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is full of wax that begins to melt at around 180 degrees F . A rod connected to the valve presses into this wax. When the wax melts, it expands significantly and pushes the rod out of the cylinder, opening the valve.


The purpose of a thermostat is to bring the water up to normal operating temperature more rapidly. The thermostat is essential in warming up the coolant before driving. Fast warm up in a passenger or performance car will reduce engine wear and fuel consumption as engines use more fuel when cold.


In racing, it is believed by some that a thermostat or a restrictor is necessary to create slow the coolant flow in the heads. The reality is that restrictors and thermostats helped the cooling process because they created pressure in the system. Today, with high-pressure cooling systems there is no longer a need to create pressure mechanically. The flow is only produced by the water pump. The pressure should be created in the radiator by turbulence and with the temperature increase from ambient to racing temperatures. Turbulence will cause the water to lap against all the inside surfaces of the cooling tubes in the radiator. A word of caution: Run a high-pressure radiator cap of up to the max pressure recommended by the manufacturer of the radiator.

 Water passage restrictors

Restrictors have been used extensively in racing as a means to increase the pressure in the engine and prevent the radiator cap from blowing off. The vernacular had it that the water needs to spend more time in the engine to pick up more heat. Race radiator manufacturers agree that water speed through the radiator and the engine is far more productive than slowing it down. Modern radiators are designed to slow down the flow of the water to build pressure.

Restrictors have been used extensively in all forms of racing. Two thoughts dominated the concept:

1-    The thought that if the water flowed too fast it would not have enough time to cool and it would leave heat from the engine behind.

2-     The belief that the restrictor or thermostat would prevent the pressure from the pump to blow off the cap pressure valve.


Racing thermostat by C&R Racing

These thermostats are produced by C&R Racing in Indianapolis, Indiana. Those units are used on all types of race vehicles but mostly where cold weather can prevail such as in Road Rally and Ice Racing.

Well, neither scenario is correct. The fast flow of coolant and air are king in engine cooling. Slow coolant flow will cause the coolant to pass through the system less often, thus picking up fewer calories (heat). Radiator manufacturers agree that neither a thermostat nor a restrictor should restrict the flow of the water- the flow created by the water pump should be restricted by the radiator turbulence in the tubes Thermostats typically open to an area about equal to the hoses in the system, permitting the water to flow somewhat unimpeded. 

In the past, radiator caps were of low-pressure design. At higher engine speeds the water pump pressure would overcome the cap pressure rating, and the water would leak out. For the past 20 to 30 years manufacturers have made radiators with crossflow designs permitting the radiator caps to be placed at the outlet side of the radiator preventing the flow and pressure from blowing off the cap. 

Do not attempt to run higher pressures than your radiator is designed for. Purpose-built radiators and their components contain reinforced tubes, and they are welded with the proper techniques to contain high pressure.

Do not pre-pressurize your cooling system. Instead, allow the system pressure to build on its own from the engine heat. If you do have a C&R system, the instruction video will guide you on how to check for air in the system by installing some pressure.


“Water flow through an engine or radiator can be compared to someone standing in cold weather with no wind blowing, compared to standing in 30 mile-per-hour wind in the same low temperature. The greater the wind/water speed, the greater the heat removal will be.




Read more →




RACING PRESSURIZED RACE CAR COOLING SYSTEMS can improve aerodynamics by allowing cars to run temperatures as high as 265 degrees.

How high can I run my water temperature?

What type of radiator can I use that will accept high pressures?

By Jean Genibrel

 C&R pressurized cooling system

Pressurized cooling systems are becoming ubiquitous in racing and off-roading.  Indy Cars, Formula Ones, NASCAR cars have used this type of cooling system for some time now with great success.Pressurized cooling systems are finding acceptance in off-road racing, short track, and road racing.

Properly designed pressurized cooling systems, such as those manufactured by C&R/PWR Racing, utilize an accumulator which is similar to a surge tank, but it is built to sustain higher pressures, and it acts as an air spring. Water accumulators contain a pressure relief valve and a sight gauge to help in bleeding the system, a line from the suction side of the water pump and a return hose from the radiator. The tank comes with a Pressure Relief Valve (PRV). The PRV is adjustable, so it eliminates the pressurized radiator cap. The accumulator is also accompanied by a quick disconnect fitting for the operator to add some pressure to check for any air trapped in the heads.

Drawing of air bubbles in head, Evans

This drawing from Evans Waterless Engine Coolant identifies the areas most prone to boiling in the heads. These spots reside above the combustion chamber and the exhaust port. Once the water reaches Critical Heat Flux, the steam creates a barrier between the metal and the coolant. This condition can lead to preignition, detonation, pinging and severe engine damage. A system with an adjustable pressure valve will permit the pressure to increase to a preset level and to avoid boiling the water.


A water pressure gauge (and warning light) can give the driver an idea where his car cooling system stands. The temperature should increases at the same rate as the cooling system pressure. When a hose blows or a leak begins, the driver can spot the problem before losing control of the car in the leaking coolant.

About Pressurized Cooling Racing Water Systems

From C&R Racing (now PWR Racing)

Pressurized water systems are relatively new to the short track and stock car world.  This technology has been around in F-1 and Indy Cars for many years.  C&R has been involved with the pressurized cooling systems through our Indy Car customers since its inception.  It’s more efficient and safer than the conventional closed cooling system that has been around for the last 80 years.  This is the future for cooling systems that will make its way into the stock car and short-track arenas over the next few years. (Since C&R published this piece, their pressurized cooling systems have made headways into off-road racing and drag racing. ed)

Pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block.  Pressure keeps the air compressed and maintains the water-to-metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads.  When a situation occurs that causes temperatures to rise such as lean fuel mixture, too much ignition advance, or a clogged radiator, the air in the water will expand and form small steam pockets.  This will start in the combustion chamber area (hottest spot) and the steam pocket will be attached to the metal surface.  These spots get very hot and since it’s in the combustion chamber area, it will create a detonation problem.  Therefore, engines lose power when overheating occurs.  Once steam starts in the cooling system, the problem will magnify and continue to get worse.

By keeping adequate pressure in the system, the boiling point will be high enough that this overheating situation can be prevented.  The higher the pressure the higher the boiling point.  For instance, at sea level with a 30 lb. cap the boiling point would be around 265 degrees.  That’s why we always recommend a 30 lb cap for racing.  With our pressurized system, we use an adjustable pressure relief valve instead of a radiator cap.  We do this because it will go higher than 30 psi.  The other components in this system are an accumulator and a tool to set the pressure in the system.  The accumulator is a can, similar to a header tank, that the air bleeds into from the cooling system and this can also has a controlled air space that acts as an air spring.  This air spring will compress under temperature expansion and keep water from going out the overflow.  It keeps the pressure in the system and is the place where the system pressure is set.

 The boiling point increases as the pressure in the system rises. The critical point to avoid is the nucleate state where the steam bubbles can explode and cause damage to the engine and create preignition. 

“If the heat flux of a boiling system is higher than the critical heat flux (CHF) of the system, the bulk fluid may boil, or in some cases, regions of the bulk fluid may boil where the fluid travels in small channels. Thus large bubbles form, sometimes blocking the passage of the liquid. This blockage results in a departure from nucleate boiling (DNB) in which steam bubbles no longer break away from the solid surface of the channel, bubbles dominate the channel or surface, and the heat flux dramatically decreases. Vapor substantially insulates the bulk liquid from the hot surface.

The pressure in a cooling system is vital for keeping water in contact with the metal surfaces of the cylinder heads and block.  Pressure keeps the air compressed and maintains the water to metal contact that is vital to prevent localized boiling or steam pockets in the combustion chamber areas of the cylinder heads.  When a situation occurs that causes temperatures to rise such as lean fuel mixture, too much ignition advance, or a clogged radiator, the air in the water will expand and form small steam pockets.  This condition starts in the combustion chamber area (hottest spot), and the steam pocket will be attached to the metal surface.  These spots get boiling, and since it occurs in the combustion chamber area, it will create a detonation problem.  Detonation is why engines lose power when overheating occurs.  Since race car cooling systems are not designed to cool steam, Once steam starts in the engine, the problem will magnify and continue to get worse.

C&R Racing manufactures most of the radiators used in NASCAR Cup racing. With those teams, C&R engineers have been able to develop a pressurized system that has allowed some engines to run as high as 290-degrees F. The system is composed of a purpose-built radiator, a pressure tank, and a pressure relief valve at the top of the reservoir. The gauge on the right is used to check for air in the system at the time of the installation. The assembly from also comes with a pressure regulator to install the small amount of pressure intended to check for air trapped in the system. The kit also comes with a quart of C&R’s Safe Coolant Corrosion Inhibitor additive.


What are the advantages of a pressurized system?

With a pressurized system, the engine can operate at higher temperatures safely.  In the case of an Indy Car or F-1 car, it means that the air ducts to the radiators can be smaller and thus more aerodynamic.  On a Sprint Cup or road race cars, tape can be applied to the grill opening making the cars more aerodynamic by reducing the quantity of air that becomes trapped in the engine compartment.  There is a bigger safety margin for error such as clogging the radiator or running too lean on fuel mix.  You can run leaner for power and not be in the danger zone of overheating.  As an example, most F-1 teams will run cooling system pressures as high as 50psi and will race all day with temps at 265 degrees.

When filled, the accumulator should contain an air space above the water level to act as an air spring.  Since water does not compress, but it expands with higher temperatures, the air spring allows the expanded water to squeeze the air without lifting the PRV. If the system is all water and no air spring is present, the PRV will lift during the temperature expansion cycle.  The PRV setting in relationship to the size of air spring, water volume, and the amount of pressure added at ambient will determine the maximum water temperature possible without opening the PRV.  Some teams are running as hot as 290°F (and 60 to 70 PSI) with the C&R system on a regular basis without opening the PRV.

The air spring possesses an additional feature. To check for complete bleeding of any air, the system is first filled with water, the engine is operated at low to medium speeds for several minutes, and the level is checked again on the gauge. A drop in the level means that there is some air in the system. 


 Fill cooling system with water and a water conditioner such as Safe Water Conditioner.  Remove –12 port plug from the top of the accumulator and top off with water.  Depress poppet on quick disconnect so that the air spring cavity will fill 75% with water leaving upper 25% as air space.  MAKE SURE THAT THE SCREEN ON THE –12 PORT BUNG IS CLEAN (Where Applicable)Click on this video for more information

  1. Run the engine with –12 port plug removed until all the air has bled out of the system.  Fill accumulator with water to the top of –12 filler leaving no air space.  Replace –12 port plug and warm the engine to approximately 180 degrees.

NOTE:  Using water circulator will help purge air from the system.

Connect pressure filling tool to quick disconnect fitting.  Increase pressure until water pushes through PRV (Approximately 35psi).  Push water out until level on sight glass is at half way point.  That point is the operating level.


NOTE: During setting the water/air spring level in the sight glass, you can see if any air is trapped in the cooling system.

If the level in the sight glass is at halfway and when adding pressure the water level drops substantially or even disappears, there is an air pocket somewhere in the cooling system.  Air will compress, causing the water level in the sight glass to drop.  The water level will return to the glass tube when you remove the pressure.

Circulate the water by running the engine or use the water circulator ( part number 60-00002 ) to bleed out the air.  When the system is properly bled, the level in the sight glass should only drop ½-inch or less upon applying pressure.

"Air will compress, water will not.”  This is an ideal way to test for trapped air. After setting the level in the sight glass halfway, bleed pressure down to 15psi.  15 psi is the starting pressure with a 180-degree engine temperature.


  1. Fill the cooling system with water.  Plug in the water circulator and circulate to remove air.  Depress the poppet on quick disconnect to bleed air from air spring cavity and fill to top of sight Fill accumulator to the top and replace –12 port plug.
  2. See step 3 under race day procedures.
  3. After setting the level in the sight glass, bleed to 5-8psi.  This will be a starting point for qualifying with a cold engine and cooling system.  This number is based on starting with a “cooled off” temperature of 50°F. publishes this handy "Boiling Point Calculator":



Do not attempt to run higher pressures than your radiator is designed. Purpose-built radiators from C&R/PWR Racing contain reinforced tubes, and they are welded with the proper techniques to hold high pressure.

Do not pre-pressurize your cooling system. Instead, allow the system pressure to build on its own from the engine heat. The C&R instruction video will guide you on how to check for air in the system by installing some initial pressure.

Read more →



Racing Performance Radiators with C&R Racing

Distilled or tap water in aluminum radiators? Which water wetter to use?

By Jean Genibrel


Racing, performance, towing and off-roading

   The cooling system is often underestimated by many race teams, owners, and especially privateers when they build or modify a racing car or engine. A team upgrading to a motor with more power or after adding more serious parts to the engine such as a bigger cam, or moving to higher compression would be best advised to build up their cooling system.

When it comes to selecting a radiator for your application, there are several factors to consider. The right radiator can make a significant difference in the performance and efficiency of your system. In this blog post, we will explore the key considerations to keep in mind when choosing a radiator.

1. What is the heat dissipation requirement?

The first step in selecting a radiator is to determine the heat dissipation requirement of your application. This is very difficult for  alayman 

So if you race a 500 horsepower small block motor in circle track, your radiator requirements will be different from those who run a 250 HP four-cylinder-car in road racing.

2. What is the size and space constraints?

Consider the available space for the automotive radiator in your application. Measure the dimensions and ensure that the radiator you choose fits within the allocated space. Additionally, take into account any size restrictions that may impact the airflow at the radiator.

3. What is the ambient temperature?

The ambient temperature of the environment in which the radiator will operate is an important factor to consider. If the ambient temperature is high, you may need a radiator with a higher cooling capacity to compensate for the increased heat load. In such a case you might consider adding an electric fan to the radiator to cool at lower speeds.

4. What is the airflow?

The airflow around the radiator plays a crucial role in its performance. Consider the airflow direction and velocity in your application. If the airflow is restricted, you may need a radiator with a higher fin density or a more powerful fan to ensure efficient heat dissipation.

5. What is the material and construction?

The material and construction of the radiator can impact its durability and performance. Aluminum radiators are lightweight and offer good heat transfer, while copper radiators provide excellent thermal conductivity but at an added weight. Additionally, consider the design and construction quality to ensure long-term reliability.

6. What is your budget?

Finally, consider your budget when choosing a radiator. While it's important to invest in a high-quality radiator that meets your requirements, it's also essential to find a balance between performance and cost. Compare different options and choose the one that offers the best value for your money. If you race the engine avoid cutting corners. An inadequate cooling system can cost a race and an engine!

By considering these factors, you can make an informed decision when choosing the right radiator for your application. Remember to consult with a radiator expert or supplier to ensure that you select the most suitable radiator for your specific needs. A well-chosen radiator will not only enhance the performance of your system but also contribute to its longevity and reliability. APPLIEDSPEED.COM offers the right balance in cost and efficiency for its radiators and oil coolers.

Drag increases as the frontal area of a radiator increases. Lift is also affected. Of course the higher the speed the greater this effect. This is why Stock Car teams tape the grill area for qualifying and when the weather cools down.


 Rock Crawlers, Jeepsters, and Dune Warriors can identify with large wheels and tires, driving in lower gears, high caster and scrub radius settings contribute greatly to creating heat. Adding towing and recovery equipment in front of small grill openings like on this Jeep do not help either. 

Radiator tube dimentions

Tube dimensions can vary greatly depending on application and manufacturer preference. The thickness of the tubes will dictate the dimension left for the fins.





 C&R is a supplier for INDY Car, NASCAR, and Formula1 among many other world class associations. The same radiators are available to the racing and performance public through APPLIEDSPEED.COM.

Other situations that warrant over-building the cooling system are in anticipation that the car or truck will be used in hot weather or run lower gears, race or drive on a muddy or icy surface or race course. These conditions will increase the engine RPM, power, and the amount of time spent in the RPM range associated with the increase in heat. 

Power is heat is power... However, advanced timing and lean air/fuel mixtures create more heat than a correctly timed engine at stoichiometric point (jetted correctly at 14 parts of air to 1 part of fuel by weight) while reducing power output. The cooling system uses up to 30% of the power the engine produces. Heat is (not always) power.

Late Model Modified C&R radiator

Late Model Modified is one of the most popular classes in circle track racing. These LMM purpose-built radiators come with a universal inlet design and a double pass system. C&R manufactures radiators and fan assemblies for road and drag racing, circle track, off road and performance cars. For off road, Jeeps, SCCA, NASA, NHRA. IHRA, NASCAR, and all other associations.

C&R pressurized cooling system

C&R produces a pressurized cooling system for racing cars and trucks. These units have allowed some teams to run their engine temperatures as high as 290 degrees without any troubles. The kit comes with a pressure relief valve that teams can set to any pressure. Formula 1 and Indy Car teams have utilized this cooling system for several years. 

 C&R Racing produces a pressurized cooling system that allows the temperature to run as high as 260 degrees.

Dirt Stock Car Racing is an example of where the cooling system could be over-built because of the real possibility of mud and dirt blocking the air intake. Off road racing cars, Jeeps and trucks cooling systems also qualify to be overbuilt.

Dirt car with mud in grillIn some forms of racing like in dirt oval track, mud and debris are an issue. Here again, over-building the cooling system favors the planners. It is easier to bring engine temperatures up than to bring them down. Off-roaders should also heed this advice.


So, if heat is power, why remove some of it? Too much of a good thing is not a good thing. Failure to maintain an engine at an acceptable temperature range will create damage such as burnt valves, blown head gaskets, cracked heads or blocks. Should an excessive amount of heat be removed from the engine, the power will drop accordingly.

Heat is power! So why remove some of it? Engines create an excessive amount of heat that we must remove to avoid engine damage. Radiators are the heat sinks used to maintain the engine temperature within an acceptable range. The purpose for a radiator is to dissipate a portion of the heat the coolant has picked up from the engine via convection. The coolant picks up the excess heat from the engine via convection, and it carries it to the radiator where the radiator tubes transfer the heat (calories) to the fins that are wedged between the rows of tubes, again through convection. From there, air, as it flows through the core, absorbs the heat stored in the fins and dissipates a portion of it to the ambient atmosphere


 In this video, C&R Racing explains how their extruded tube OE fit radiator modules with Spal fans add up to the ultimate for your ride for added cooling and strength.

Radiator thickness affects cooling depending on the air flow.

Thicker radiators cool better if they have enough air flow. Between a thick and thin radiator with low to moderate but equal air flow, the thinner radiator will very likely perform better. So if you have a street/drag car you may be well off with a radiator on the thinner side and if you road race or circle track your car opt towards a thicker radiator. A high fin count can make a cooling setup loud if the air flow is high enough.

Modern manufacturing techniques have improved quality of race radiators

The better race radiator manufacturers employ all the modern technology to produce a durable, effective and cost efficient product. Lean Manufacturing improves speed and reduces waste. Toyota Motor Company has pioneered Lean Manufacturing, and it has become the standard for many industries. Six Sigma Quality techniques originated in the aerospace industry and are used to prevent defects further. Each process is tested scientifically for possible failures and failures are prevented rather than being repaired. Manufacturers like C&R Racing use Computer Aided Drafting and Computerized Numerical Control to achieve tolerances of .005" to be maintained providing complete repeatability and reliability. 

C&R Sprint Car Radiator

 Furnace brazed cores ensure peak performance for years and eliminates the need for epoxy. Moreover, aggressive fin counts for all applications assure maximum cooling. Aggressive fin counts are more expensive and are therefore not used widely in the industry, but Griffin Radiator Company’s  racing experience has determined that it maximizes cooling capacity for the hard to cool applications.



Radiators (coolers) offer the advantage of taking the heat to the air. With air-cooled engines, we must transport the air to the heat. A disadvantage Porsche had overcome with clever ducting until engine power (heat) began to compete with aerodynamics and loss of power from trying to pump air. More can be said about the wicked aerodynamic consequences of managing a medium that we cannot see or feel, and at very high velocity becomes the density of molasses.

Never mount radiators or coolers without rubber support to absorb vibrations and chassis twist. Solid mounted radiators will crack in short order.


Aluminum is a wonderful metal but its weakness is that its low density makes it prone to cracks and breaks when placed under repeated vibrations. A radiator full of water, its hoses, brackets and possibly a fan can add up to a considerable amount of weight hanging on the mounts. As such, it is imperative that radiators never be mounted solidly in the chassis.


Radiator mounting

Radiators should be installed in such a way to allow easy and quick removal of the cap and to make filling with the coolant a clean and easy task.




Rubber mountsRemember that soft mounting applies in all forms of racing.  Damping sandwich mounts are available from These mounts screw into mounts and flanges to create a vibration proof environment for coolers and radiators. The mounts must be installed in support with the studs, vertical, not in shear.


The best way is to mount radiators is on soft material like rubber, foam, grommets, or other material that will isolate the radiator or cooler from the chassis vibrations and flex. In off-road racing or Circle Track Dirt, the environment is so abusive that a solidly mounted radiator will only survive a few minutes on a rough course. In road racing, circle track and drag racing the rule still applies.


.     With some radiators and coolers, you can fabricate a cradle lined with thick foam rubber to support the lower tank. The upper cradle can be made in a similar fashion, and it can just clamp on top of the radiator. Note: Allow the radiator to remain loose in the foam rubber to avoid stressing the core


Side tank radiators require brackets or studs to be mounted properly. The brackets will also need to be mounted on some soft material. Studs can be mounted on rubber isolators.

Image shows upper bracket with a stud. Rubber grommets are affixed over the stud, and the grommet slips into a hole inserted into a mount.

What Type of Water Should I Use in my Aluminum Racing Radiator?

Is Distilled Water the Best for Racing Radiators?

What about “water wetters”?


Some believe that using the wrong type of water without the proper additive can facilitate electrolysis where the ion depletion of the aluminum can create holes and leaks. While in some instances there is some truth to this claim, the reality is that using perfectly pure water (distilled, etc.) at the temperatures race cars operate, would cause minute, if any, damage. (“Guidelines for Use of Aluminum with Food and Chemicals”). Pure water (from distillation, deionization or by reverse osmosis) is free of solutes and salts. These solutes balance the PH in the water, and they offer a buffer to prevent the water from craving ions from the aluminum.



Some racers have the luxury to carry spare radiators and water. The cooling system in rally and off-road racing must be as reliable as those in a stock car or Sprint Car. There, the judicious choice of the type of water and its additives is paramount as it is in all forms of racing. Heed the “be prepared” advice when you go out in your Jeep or just sightseeing in the desert.

Tap water is the most readily available. The problem with tap water is that it is always unknown what types of minerals and in what quantities are contained in it. Well-water falls in the tap water category. Tap water can be utilized in race radiators if they have the proper additive installed. Tap water will leave residuals behind if the water is often drained or if it boils out of the system. Otherwise, the volume of solids contained in tap water is minimal.

Water, when heated, drives off a significant proportion of dissolved oxygen, but it reabsorbs fresh oxygen as it cools. This cycle leads to a perpetual cycle of corrosion, which is accentuated in cooling systems with no expansion tank.

Water also acts as an electrolyte if dissolved solids, such as hardness salts (lime scale), etc., are present. Salts promote galvanic corrosion where metals of high nobility sacrifice themselves to metals of lower nobility – this is often manifested by pitting. To avoid electrolysis, the radiator must be isolated from the rest of the vehicle and the electrical components, like electric fans and rotating components like transmissions, should be grounded to the frame, not the radiator. More reasons to mount radiators and coolers on rubber isolators.

 Distilled water is the purest form of water available. Distilled water is fully devoid of any minerals and other impurities. Distilled water is produced by boiling water and recapturing the steam. When the steam is cooled, it returns to water in its purest form.

The water in a radiator attacks steel, copper, and aluminum. Using distilled water and antifreeze is always the best approach to preventing corrosion. We can use tap water if we combine it with the proper amount of antifreeze, and, or, the correct water wetter. The type of water used is immaterial if it is mixed with the right additive. Photo courtesy Evans Cooling.


Evans Cooling Systems, Inc produces an engine coolant that Evans Chemists say never needs replacing and requires absolutely no water. In fact, ECS emphasizes that any water added in conjunction with their coolant will void their warranty as the water can produce steam pockets that can cause serious problems. The product is composed of a patented blend of ethylene glycol and propylene glycol with proprietary additives. Also, the coolants include other glycols to achieve their high boiling point and to eliminate the need for replacement.


Evans produces coolants for high performance, powersports and heavy duty, each product using a slightly different formulation to meet the environment. Jeeps, Fords, Chevrolets, Chryslers, Hondas, Toyotas, BMWs, and all other makes owners can find Evans Cooling Products at


Distilled water is a good choice for used aluminum radiators. If you install a new aluminum radiator just to check for leaks and you run distilled water through it, before the radiator is stored it must be dried thoroughly inside and out. Otherwise, run the motor for several minutes, or run a race before removing the radiator. This will prevent passivation and the possible leaks this process can cause. See the subject of "passivation" in this blog.



We must emphasize that some “wetters” do not contain the chemicals necessary to use with distilled water. The requirement with some products to use a tap water is due to the utilization of a corrosion package that doesn’t provide sufficient protection against the more reactive distilled water. Antifreeze is always safe to use with tap or distilled water if you race on dirt or your association allows it. Antifreeze contains all the anticorrosive agents to protect aluminum and iron, but not all the “wetters” contain all the additives for tap and distilled waters.

For racing, if no antifreeze is allowed, or if one chooses not to run antifreeze, tap or distilled water he may use Red Line’s Water Wetter. Water Wetter contains all the chemicals needed to bring distilled water to the right PH and equalize the ion craving effect of the water. Royal Purple’s, “Purple Ice,” and Lucas’ “wetter” are formulated for use in tap water only, as the products rely on some of the chemicals in the tap water to balance out the PH. C&R recommends its additive for use with distilled water only.  Amsoil’s “Dominator Coolant Boost” is not to be used with distilled water unless mixed with 50% antifreeze.

Red Line Water Wetter

Red Line’s Water Wetter contains all the minerals needed to neutralize distilled water, and it can also be used with tap, or distilled water. To avoid confusion just use tap or distilled water with the right quantity of Red Line Water Wetter.











 Always rely on the radiator manufacturer’s recommendations before filling the radiator with water, antifreeze or any additives like water wetters. Manufacturers may use different aluminum alloys that may have a different reaction to one water over a variant.

When using straight water with a new radiator never fill it and then drain it before having run the motor for several minutes. Letting a new radiator sit when still wet will cause the ion migration to eat small holes in the aluminum, turning the radiator into a garden sprinkler. Allowing the radiator to “cure” by leaving the hot water in the radiator, or running the car for a race, will cause the aluminum to form a thin barrier of oxide. This process is known as “passivation.” Once passivation has taken place any clean water we can use any water in the aluminum radiator.






Read more →

Racing and Performance Water Pumps

Racing and Performance Water Pumps

Edelbrock water pumpEdelbrock water pumpRacing water pump


How high can I rev my stock water pump? Will my engine run cooler with a high performance water pump? Can water pumps increase the power output of my engine? How much power does a water pump use? How much power can I save with a  racing water pump like one from Edelbrock?Performance racing water pump? What should I know?


O.E.M. parts are made for street use and not for racing. Some racing parts like some cams, pistons, transmissions and many others should not be used in racing, and water pumps are no exception. Some manufacturers produce dual purpose high performance and racing water pumps. Much like choosing any other part of a street, performance or racing car, good judgment and doing some research aims high at attaining the desired results from a water pump. Water pumps are very simple components but pushing one beyond its designed limits can be as catastrophic to an engine as running out of oil or water. A stock water pump will not pump sufficient water for racing. 



The water pump is called upon to create a flow of the coolant through the engine (the heat source) where it can pick up excess heat and transport it to the radiator (heat exchanger). Then, the radiator (the heat sink) transfers the heat to the air, all with the least amount of power loss from the engine.


racing and performance water pump diagram

    An automotive water pump is a relatively simple component, yet, like all the other elements of a race car if any one of its parts is not doing its job or it is not up to the task the pump will not work properly. A water pump problem can cause catastrophic failures in the range of a blown head gasket to a complete engine breakdown. Drawing courtesy of ASC Industries


    The flow from the water pump meets the radiator, the thermostat or the restrictor, which pressurizes the water in the engine [in addition to the pressure created by the expansion of water] to keep the boiling point in the motor as low as possible.



    In the heads, above the combustion chambers and around the exhaust ports, localized boiling can occur, particularly within the irregularities of the casting surfaces.  This process, known as nucleate boiling, ( does not necessarily have an adverse effect at low engine speeds, but if left unchecked, at higher RPM it can create some serious problems. Since air does not absorb or release heat as well as water the air bubbles can form hot spots, detonation, and loss of power. Problems start when nucleate boiling morphs into film boiling, where the bubbles converge to form a film of steam. This process, “Departure from Nucleate Boiling” ( can be so violent that it can crack cylinder heads and blocks.

     Nucleate boiling in racing engines

    Drawings illustrate the importance of pressure in the cooling system. Notice that boiling is not necessarily a problem. It is when the temperature reaches the nucleate point that vapor bubbles explode. Since steam does not gather heat as efficiently as water, the surfaces above the combustion chambers will not cool properly, and the engine will experience pre-ignition. The forces dissipated by the explosions can create cracks and blown head gaskets

    Racers often install a thermostat or a restrictor in racing engines. In racing, this practice is no longer necessary as modern purpose-built radiators are designed to build the pressure through their tubes (turbulation) that will, in turn, create pressure in the block and heads. What is more, the expansion of the water should create sufficient pressure in the system to keep the water from boiling at higher temperatures. Thin radiators or double-pass radiators also restrict the flow sufficiently to create pressure. An undesirable effect can occur if a low-pressure radiator cap is used without a thermostat or a restrictor plate the pressure may blow off the relief valve on the radiator cap pressure.

    The impeller in the water pump is responsible for creating the flow. The pressure is created by the restriction of the radiator tubes. The expansion of the water due to temperature increase further raises the pressure. Getting the most work from the impeller is the key to having an efficient pump. When over revved or when worn out a stock water pump will cavitate.

    Stock water pump impellers

    Stock water pumps are not precision pieces like Edelbrocks' or Stewart Components'. The impellers are stamped pieces that do not always meet racing requirements. Furthermore, auto parts pumps' bearings do not meet high performance requirements. Racing pumps sport O-ring seals that negate the need for sealant.



    Water pumps with steel impellers can be improved by adding a plate on the impeller to form a tight pocket for the water to accumulate. The impeller can be driven down to a clearance of about 25 thousands of an inch with a small hammer and a socket. Race and performance water pumps like those from Edelbrock run tighter clearances yet, but their tolerances are super accurate and they should not be attempted on auto parts pumps. If you wish to blueprint your stock water pump insert a feeler gage between the impeller and the pump body to set the clearance.

    Blueprinting a water pump

    It is often incorrectly believed that a pump [or a boat propeller] that cavitates creates air bubbles. The bubbles are composed of steam. What happens is when the pressure drops in the back of the impellers the boiling point of the coolant solution decreases until it reaches boiling. Bringing the impellers close to the pump body reduces or eliminates the cavitation. 


    Cavitation is the formation of vapor cavities in a liquid – i.e. small liquid-free zones ("bubbles" or "voids") – that are the consequence of forces acting upon the liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shockwave. These shock waves can be intense enough to damage a water pump, crack a block or a cylinder head.

    Setting the impeller gap to improve water pump flow

    The space between the water pump impeller and the pump body must be kept very tight. Reduced clearance at the impeller prevent the creation of eddy flows, and it can improve coolant flow by as much as 15% while keeping the engine running cooler. What is more, a tight impeller will create some additional pressure in the heads further reducing the water boiling point and the risk of detonation. A plate such as the one in this photograph will also improve flow, but remember that stock water pumps are not made for racing, and they are not recommended for a race or high-performance vehicle.


    With stock water pumps, cavitation can occur at increased engine speeds such as when a stock engine has been built to produce more RPM. Cavitation is the formation of vapor (steam) bubbles in the cooling system. These bubbles form when the coolant temperature reaches the boiling point determined by the pressure that is present in the cooling system.

      Flow and power improvement graph Edelbrock racing water pump

    Stock water pumps can rob more power than necessary. This dyno test shows a near 5 horsepower gain by using a well-designed pump. Edelbrock racing pumps save as much as seven horsepower with a bonus of 17-degree cooler temp.


    Eddy flows are caused by an excessive distance between the impeller and body of the pump. The distance can be from poor quality control on the part of the manufacturer or corrosion. There, the water becomes pressurized, and as it attempts to escape between the blades and the pump body it creates “eddy flows.” This phenomenon imparts axial vibrations that can damage the seals and the bearings as well as increase the temperature of the water. What is more, the turbulent flow will also reduce the movement of the water and the pressure in the engine.


     Racing water pumps such as those produced by Edelbrock put out some 30 percent more flow than stock ones. This improvement is primarily accomplished using purpose-designed and oversized cast powdered metal impellers held at tight clearances against the pump body.

    Precise machining practices are essential to maintaining the hubs and shafts perfectly perpendicular to the body to eliminate excessive bearing load, noise and to reduce power losses and heat.

    Proper manufacturing and assembly practices also yield tight tolerances between the impeller and the pump body. Most aftermarket manufacturers use high-grade bearings that are heat-treated carbon or carburized steel. The highest forms of racing such as in NASCAR Sprint Cup, Indy Car, Formula 1 and World Endurance utilize ceramic bearings that have nearly no friction and they create no heat.

    Some pump manufacturers like Stewart Components offer heavy-duty versions of water pumps for domestic and imports. All the heavy duty pumps vary in enhancements as some are for performance and some are for severe usage. HD vs. standard can sometimes affect the appearance of the pump. With the HD pumps support ribs, may be added to the bearing tower. The material used to make the housing may be cast iron or aluminum. While they may look different, they will bolt right up and fit perfectly. Most of the other enhancements cannot be seen such as better bearings, improved design impeller for greater flow and upgraded seals.

    Victor Series Edelbrock racing water pumps


    Edelbrock water pumps should not be run over 5/8 the speed of the engine.  When properly installed the water pumps will flow twenty percent more water over stock units. 

    Edelbrock racing water pump Victor series

    When tested, Edelbrock water pumps showed a temperature drop of a minimum of 17 degrees over stock or otherwise performance pumps and a reduction of 10 percent in parasitic drag.


    Seals are rated by the pressure they must contain, the shaft diameter and its speed in feet-per-second of rotation. All aftermarket replacement pump manufacturers do not always heed those requirements. Edelbrock racing and performance water pumps are equipped with the highest grade bearings and seals to endure the pressure, temperature and shaft speed of NASCAR-CUP cars. The water temps on those cars can reach 285 degrees under pressures of 60 PSI.


    Some advice from ASC Industries and Water Pump University

    Fans, Clutches, and Spacers
    The goal of any retrofit is to get the fan spaced into the shroud for max cooling, but be careful how you get there. Most manufacturers never offered a spacer and fan clutch combination. A fan spacer by itself or a fan clutch by itself is OK, but when used in conjunction the outcome can be catastrophic. When you choose a spacer be sure it is a snug fit on the shaft, and never stack spacers. Always remember that the pump was designed using a factory fan and clutch, and any variation from that will cause an additional load on the pump's bearing. The extra load can shorten the life of the pump's bearings and seals. Make sure that all components being used mate well with each other. Any misalignment or vibration in the components mounted in front of the pump will shorten the life of the pump's bearing and seal, and will in some cases cause catastrophic failure where the housing of the pump fails - causing extensive damage. 


    Hub Height

    The hub height will determine the location of the pulley and the belt. When using a Gilmer belt arrangement plan to run the hub near the center of the pulley. Image courtesy of ASC Industries.

     Water pump hub heigth measurement

    The hub height is measured from the base of the gasket surface to the top of the hub where the pulley will bolt on.

    When choosing a pump, it is important to assure that all the pulleys line up. One other thing to keep in mind is the bolt circle on the hub that the pulley and fan will bolt onto. There are several different sizes, both metric and standard, and this applies to the threads as well.  


    Most V8s built in the 60's and 70's came with a power range between 185-375hp. With the availability of all the aftermarket performance components available it is easy to greatly improve power over stock.  Originally installed water pumps were not designed for this additional power and the increased demand on water flow. Using the wrong pumps can cause spectacular failures.

    Aftermarket manufacturers such as Edelbrock manufacture water pumps that are purpose-made for racing and performance. These pumps save as much as 5 horsepower and reduce coolant temperatures by as much as 17 degrees.

    Edelbrock impeller Edelbrock's racing water pumps include precision cast impellers with extra large veins to maximize the flow rate. This type of impeller allows running super tight clearances that improve flow and pressure.


     Edelbrock’s pumps include:

    1. Precision-cast powdered-metal impellers with extra-large vanes to maximize the flow rate, ensuring adequate pressure and volume even at lower engine speeds.
    2. Extremely tight clearances between the impeller and the pump body prevent cavitation and eddy flows.
    3. Aggressive 3.45-inch impellers eliminate cavitation.
    4. Improved ports produce maximum flow, pressure and even distribution to each side of the engine.
    5. Large, high-quality roller bearings on steel shafts to prevent deflection and possible contact of the impeller with the pump body.
    6. Standard and reverse rotation pumps are available for most Chevrolets, Fords, and Chryslers.




    Read more →




    "Every transfer of heat between two fluids, like water to air, is directly proportional to the mean temperature difference between the two fluids, to the area of the interface (the cooler area) between the two fluids and the volume of the cooling fluid flow." Carroll Smith, Tune to Win

    Here are some tips that can help in understanding cooling the water or oil of a racing engine.

    • Pick up the air flow from the grill area where the highest air pressure location on a car or truck is located. With proper ducting to the radiator, it provides maximum performance. 

    Pick up the air flow from the grill area. There resides the highest air pressure location on a car or truck, and with the proper ducting to the radiator, it provides maximum performance. Without a duct, air pressure builds in front of the radiator, and it spills over into the engine area. This dynamic spoils the internal aerodynamics, increasing lift and drag, and it severely affects cooling. 

    Keep the fins of the radiator straight to avoid blocking the air flow. Fin combs are available from radiator shops or APPLIEDSPEED.COM.



    Keep aluminum radiators unpainted and clean of debris and dirt for best results. The paint acts as a thermal barrier to heat. No, the color black does not help to dissipate heat.



    • Keep the fins of the radiator straight to avoid blocking the air flow. Fin combs are available from radiator shops or APPLIEDSPEED.COM.
    • In racing situations and with performance engines, it is best not to use any “antifreeze and summer coolant.” Antifreeze prevents the water from freezing, but as far as keeping water cool it does nothing. In fact, antifreeze increases the water temps. The product is very viscous, and it increases the surface tension of the cooling medium. The added viscosity reduces the flow of the coolant in the system
    If you race on pavement, your association probably does not allow you to use antifreeze or other forms of glycol coolants. With these products, a simple leak can slick down the track and create an ideal condition for a wreck.
    • Do not paint heat exchangers. The paint acts as a thermal barrier. No, the color black does not help to radiate heat.
    • If you installed a new radiator and decided to remove it for storage, dry it off inside and out to prevent corrosion. Drops of water will attract the ions from the aluminum, and they can turn the radiator into a  sprinkler.

    Radiator fin combs come in a variety of shapes. They fit most fin spacing. A fin comb can make a great addition to the race tool box. This one is available from APPLIEDSPEED.COM.




    • Always protect both sides of a radiator with thin plywood when not racing. Those planks also help to bring the temps up more rapidly before going out on the track. Of course, remember to remove the plywood before racing.

    Stant Racing Division manufactures high-pressure radiator caps that go up to 31 PSI.

    • It all works together. As such, the flow from the water pump must be up to the task. A purpose-built water pump, like those produced by Edelbrock, pump about twice the volume of water without cavitating. Heat rejection increases proportionately to the pressure and turbulation within the cooling system. Higher flow rates witness better heat rejection, particularly with double-pass core configuration radiators. 

    Edelbrock manufactures high performance and racing water pumps that improve flow and eliminate cavitation. Do not attempt to race with a stock water pump as those only lead to overheating and possibly other serious engine troubles.

    For racing and performance use welded aluminum racing radiators like this one on the left from C&R Racing at Plastic radiators are not made to hold the pressure seen in competition, and they tend to leak at the seams like the one in this photograph.

    •  Attempt to achieve the biggest difference in temperature possible between the water in the radiator and the ambient air.  The radiator exchanges heat with the ambient air, the more significant the difference between the two, the more heat that it can reject.
    • The radiator core must be fed with plenty of ambient air. See sections on radiator ducts and fans.
    • To protect the engine from possible detonation, overheating, and catastrophic failure design a system that can allow the pressure to rise as high as necessary without the cap releasing pressure.
    • Use the type of water suggested by the radiator manufacturer and when using antifreeze always follow manufacturer’s recommendation or use the pre-mix.  Whether you run straight tap water or distilled always install a bottle of Redline’s “Water Wetter” as it contains minerals that prevent ionization of the aluminum in the radiator.

    Always mount radiators and coolers on soft rubber. When solidly mounted the vibrations can cause cracks, and a failure can ensue.










    Radiator external corrosion from soapOffroad vehicles can gather some interesting trophies on their radiators. Whether you are a full-on racer, you tow a trailer, or you just like Jeeping and camping, it is important to keep an eye on the radiator. Occasionally flush it out from the back with a spray of water. Avoid getting soap on the aluminum as the stuff will cause corrosion that creates a barrier to the incoming air flow.




    External corrosion from soap on radiator

    • External corrosion can occur on aluminum radiators. This problem is usually caused by soap from car washes. Hose off the radiator fins with a low-pressure stream of water to flush out the fins from the inside.
    • If you run straight water for racing make sure there is plenty of pressure in the system to avoid boiling and corrosion. 
    • Do not ground radiators. Instead make sure all the electrical components, the engine, transmission, and differential are grounded to avoid electrolysis and galvanization.


    Ron Davis Radiators offer this Master Grounding kit. The kit is intended to ground all the electrical components as well as the transmission, differential and engine to prevent electrolysis which can lead to galvanization in the radiator.




    Read more →

    Water in racing radiators, can it damage the aluminum and create leaks?

    Water in racing radiators, can it damage the aluminum and create leaks?

    What Type of Water Should I Use in My Aluminum Racing Radiator?

    Is Distilled Water the Best for Racing Radiators?

    What about “water wetters”?

    By Jean Genibrel

    Copper radiators were the norm years ago before aluminum became more affordable and welding, and brazing aluminum techniques grew more mainstream. Aluminum radiators have become ubiquitous in racing due to their affordability, light weight, and availability. However, the use of aluminum has opened some debates whose answers have remained unclear, to completely unsolved. The major question that still gnaws at every racer is: “What type of water should I use in my racing aluminum radiator?”

     It is possible that using the wrong type of water without the proper additive can facilitate electrolysis where the ion depletion of the aluminum can create holes and leaks. While in some instances there is some truth to this claim, the reality is that using perfectly pure water (distilled, etc.) at the temperatures race car cooling systems operate would cause minute, if any, damage. Pure water (from distillation, deionization or by reverse osmosis) is free of solutes and salts. These solutes balance the PH in the water, and they offer a buffer to prevent the water from craving ions from the aluminum. However, these solutes can create deposits and enhance corrosion.


    Rally Truck and radiators

    Some racers have the luxury to carry spare radiators and water. The cooling system in rally and off road racing must be as reliable as those in a stock car or Sprint Car. There, the judicious choice of the type of water and its additives is paramount as it is in all forms of racing.

    Tap water is the most readily available. The problem with tap water is that it is always unknown what types of minerals and in what quantities it contains. Water from wells falls in the tap water category. Tap water can be utilized in race radiators if they have the proper additive installed.

    Soap from car washes is the primary culprit for external radiator corrosion. Corrosion will eventually puncture the radiator, and the buildup on the outside reduces air flow.

    Water, when heated, drives off a significant proportion of dissolved oxygen, but it reabsorbs fresh oxygen as it cools. This cycle leads to a perpetual cycle of corrosion, which is accentuated in cooling systems with no expansion tank.

    Water also acts as an electrolyte if dissolved solids, such as hardness salts (lime scale), are present. These products promote galvanic corrosion where metals of high nobility sacrifice themselves to metals of lower nobility – this problem often manifests itself by pitting. To avoid electrolysis the radiator must be isolated from the rest of the vehicle and the electrical components, like electric fans and even rotating components like transmissions, should be grounded to the frame, not the radiator.

     Filtered and reverse osmosis waters are filtered by some means to remove the larger impurities but not all the minerals. This process is similar to filtering coffee through a paper filter.

     Distilled water is the purest form of water available. Distilled water is fully devoid of any minerals and other impurities. Distilled water is produced by boiling water and recapturing the steam. When the steam is cooled it returns to water in its purest form. Rainwater is another form of distilled water.


    “The book “Guidelines for Use of Aluminum with Food and Chemicals”, Aluminum Association, 1994, Pennsylvania State University informs us that “in high purity water, laboratory tests show that a slight reaction occurs originally between the aluminum and alloys and distilled, deionized and uncontaminated rain water, but after a few days the reaction ceases and the aluminum pickup becomes negligible.” The book further explains that at elevated temperatures of around 200C (390F) and above, both distilled and deionized water cause severe corrosion of most aluminum alloys. [However, radiator tubes being very thin (.013’’) the damage that can be done in a “few days” can be sufficient to damage the radiator. So follow the passivation instructions outlined in this post and passivation is also the subject of its own posting.]


    Many factors influence the selection of water that we can use in a race aluminum radiator. Chief among them is the type of additive that will, or not, be used in the water. Antifreeze is an additive. Using tap water may be OK in some parts of the country but in others the water may contain high levels of minerals that, in time, may cause deposits in the cooling system. Distilled water will attract aluminum ions to balance its PH level creating aluminum depletion that would be temporary and minimal. The type of aluminum the manufacturer has used can also be a factor. The radiator core tubes are typically the thinnest material in the circuit at approximately .013" thick, so it does not take long for the radiator to develop leaks if the wrong type of water or additive is used or if the radiator is not “cured” properly for passivation. Checking with the radiator maker is always the best approach to choosing the best type of water and additive for your radiator. The following information from the Aluminum Association may help clarify the subject.


    The water in a radiator attacks steel, copper and aluminum. Using distilled water and antifreeze is always the best approach to preventing corrosion. Tap water can be used if it is combined with the proper amount of antifreeze, and, or, the correct water wetter. The type of water used is immaterial as long as it is coupled with the right additive. 


    Or should the question be? “What type of additive should I use in my water?” It does not matter what type of water you use as long as you use the right additive for the type of water used. And antifreeze is an additive. So ask the additive and the radiator manufacturer for their recommendation. Generally, distilled water will be a good choice for used aluminum radiators. 


    If you install a new aluminum radiator just to check for leaks, before the radiator is stored it must be dried thoroughly inside and out. Otherwise, run the motor for several minutes, or run a race before removing the radiator. This will prevent passivation and the possible leaks this process can cause. 

    Read more →



    The piston pin offset can make for an interesting approach when rules do not permit different length rods. Offsetting the wrist pin in the piston has the same effect as lengthening or shortening the rod. Adjustments in piston compression height must be addressed to maintain the original compression ratio and to prevent piston contact with the head.

    Read more →