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.




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