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Understanding High-Volume Oil Pumps and Their Role in Engine Performance
High-volume oil pumps are designed to move significantly more oil through your engine compared to standard pumps. They have larger gears to move more oil per revolution, typically delivering 15 to 20 percent more oil than a comparable stock pump. This increased flow can provide critical benefits for certain engine configurations, but it’s not a universal solution for every application.
The fundamental purpose of any oil pump is to create flow, not pressure. The oil pump creates a flow of oil to the engine, and the restrictions in the oil passages of the engine produce the pressure. Understanding this distinction is essential when evaluating whether a high-volume pump is right for your build.
For most stock or mildly modified street engines, a standard oil pump provides adequate lubrication. Standard pumps will provide enough flow and pressure for stock to moderate performance engines. However, when engine demands increase—through higher RPM operation, larger bearing clearances, or additional oil system components—a high-volume pump becomes necessary to maintain proper lubrication.
How High-Volume Oil Pumps Work
The design of high-volume pumps centers on moving more oil per pump revolution. They have taller gears with a larger surface area so they can pump a higher volume of oil. This increased capacity allows the pump to deliver more oil to critical engine components, particularly at higher engine speeds where oil demand increases dramatically.
Most high-volume pumps also incorporate pressure increases to help deliver oil more quickly to bearings and other components. Most high volume pumps also have an increase in pressure to help get the oil out to the bearings faster. This combination of increased volume and pressure can be particularly beneficial in high-performance applications.
The pump’s output is directly related to engine speed. The oil pump’s volume is proportional to engine speed, so that the higher the rpm, the higher the oil volume. This means that at elevated RPM, even a standard pump moves substantial amounts of oil—but a high-volume pump moves even more, which can be critical for engines that spend extended periods at high RPM.
One important consideration is cavitation at high engine speeds. Most double spur gear crankcase mounted stock oil pumps flat line above 5,000 RPM due to cavitation. High-volume pumps with improved designs can help overcome this limitation, maintaining adequate flow even as engine speeds climb beyond typical street driving ranges.
Key Advantages of High-Volume Oil Pumps
Enhanced Lubrication for High-Performance Applications
The primary benefit of a high-volume oil pump is improved oil delivery to engine components under demanding conditions. These pumps are good for performance engines with larger bearing clearances. When bearing clearances are opened up for performance applications, more oil is required to fill those gaps and maintain proper lubrication.
Increased oil flow becomes essential when engines are modified with specific components or operating conditions. Increases in the engine’s oil requirements come from higher rpm, being able to rev faster, increased bearing clearances, remote oil cooler and/or filter and any combination of these. Each of these modifications increases the engine’s oil demand, and a high-volume pump helps meet that demand.
For engines that operate at sustained high RPM, the benefits become even more pronounced. If you have an engine that can rev beyond 6,000 RPM or higher, a high performance high volume oil pump would probably be a good upgrade and provide added lubrication insurance. Racing applications, particularly circle track or road racing where engines run at high RPM for extended periods, benefit significantly from the increased oil flow.
Better Oil Pressure at Low RPM
An often-overlooked advantage of high-volume pumps is their performance at lower engine speeds. The high volume pump is useful in a way that most people don’t think about: it will keep higher pressure into the engine at low RPM’s and idle. This can be particularly valuable for engines with larger clearances that might otherwise suffer from low oil pressure at idle.
The increased flow capacity means that even at idle speeds, the pump can maintain adequate pressure to protect engine components. The increase in oil flow produces an increase in oil pressure at idle, which helps compensate for increased bearing clearances. This characteristic makes high-volume pumps attractive for engines that have accumulated wear or were built with intentionally looser clearances.
Improved Heat Management
Oil serves dual purposes in an engine: lubrication and cooling. Increased oil flow in a present day water-cooled engine can also help cool and prolong the life of the main and rod bearings, and increase splash lubrication to the undersides of the pistons. The higher flow rate from a high-volume pump means more oil circulates through the engine, carrying away heat more effectively.
This cooling benefit becomes particularly important in high-stress applications where heat generation increases dramatically. The additional oil flow helps maintain lower bearing temperatures, which extends component life and reduces the risk of oil breakdown under extreme conditions.
Potential Drawbacks and Considerations
Excessive Oil Pressure Risks
While increased oil flow can be beneficial, excessive oil pressure creates its own set of problems. High oil pressure can damage seals and gaskets, leading to leaks throughout the engine. In extreme cases, high-pressure pumps can blow oil filters off, creating dangerous situations and potential engine damage.
The relationship between pressure and engine protection is often misunderstood. High oil pressure WILL NOT “wash out” your bearings. Excessive heat from low oil flow will overheat and destroy your bearings. The key is maintaining adequate flow, not simply maximizing pressure. Too much pressure without corresponding flow needs can actually create problems rather than solve them.
It’s important to limit maximum oil pressure to safe levels. It is important to limit max oil pump pressure to around 100 PSI to prevent blowing out gaskets and seals. Beyond this threshold, the risks of component failure increase significantly, and the additional pressure provides no lubrication benefit.
Compatibility Issues with Stock Components
High-volume pumps can create problems when installed in engines with tight bearing clearances designed for standard oil flow. If you put a high volume pump into an engine with tight clearance, you may end up with high oil pressure up to the point of where the relief valve opens and some of the oil flows under pressure directly back to the sump (lost power). This situation wastes energy and provides no lubrication benefit.
The increased load from a high-volume pump can also stress the pump drive system. On some engines, particularly Fords, Ford gears tend to get eaten-up because they just aren’t big enough or strong enough to take the additional load that a high volume pump puts on it. This can lead to distributor gear failure and subsequent cam damage, creating expensive repair situations.
Stock oil pans may not have adequate capacity to handle the increased oil flow. A high volume oil pan would also be recommended so the pump doesn’t suck the pan dry at sustained high speed. Without sufficient pan capacity and proper baffling, the increased flow can lead to oil starvation issues, particularly during hard acceleration or cornering.
Windage and Power Loss
One of the most significant drawbacks of high-volume pumps is increased windage. Windage is parasitic drag on the crankshaft due to sump oil splashing on the crank train during rough driving. It can also be dissipating energy in turbulence from the crank train moving the crankcase gas and oil mist at high RPM. This parasitic loss directly reduces available horsepower.
The increased oil volume circulating through the engine creates more opportunities for windage losses. When unchecked, windage can cause oil pressure and oil temperature problems in addition to power loss. At high RPMs the spinning crank can draw in and throw the oil draining from your engine back against the block. This creates a cascading effect of problems including increased oil temperature, aeration, and reduced efficiency.
The power loss from windage is not insignificant. Dyno testing shows again and again that it robs real horse power from the engine. For maximum performance applications, this trade-off must be carefully considered. In some cases, the lubrication benefits outweigh the power loss, but in others, a standard pump with proper clearances and oil viscosity may be the better choice.
Increased Oil Temperature
Higher oil circulation rates can lead to elevated oil temperatures. They also raise the oil temp since the oil is circulating at higher volumes. The increased flow means oil spends less time in the pan cooling and more time circulating through hot engine components, which can raise overall oil temperature.
Aeration compounds this problem. Aerated oil doesn’t dissipate heat at the same rate as clear liquid oil. Increased oil temperatures in the system lowers the actual viscosity of your oil, which reduces the oil’s ability to properly do its job within the engine. This creates a negative feedback loop where higher temperatures reduce oil effectiveness, potentially requiring thicker oil or additional cooling measures.
Choosing the Right Oil Pump for Your Engine
Assessing Your Engine’s Needs
The decision to use a high-volume pump should be based on specific engine characteristics and intended use. Bearing clearances are the primary consideration. The reason performance and race engines use them is because the clearances are upwards of twice the amount as a stock engine. Those voids flow oil out much quicker so they need more volume to stay filled with oil.
Traditional bearing clearance guidelines suggest approximately 0.001 inch of clearance per inch of journal diameter. Traditional thinking has bearing clearance for street and most performance applications at roughly 0.001-inch of clearance for every 1-inch of crankshaft journal diameter. Engines built to these specifications typically work well with standard oil pumps.
However, when clearances are opened up for performance applications, oil requirements change dramatically. Wider bearing clearances do require a heavier viscosity oil (such as a 20W50 multi-viscosity oil or a straight 30, 40 or 50 oil). The heavier viscosity oil is absolutely necessary with wider clearances to maintain the oil film between the bearing and shaft so the bearing isn’t starved for lubrication. In these cases, a high-volume pump becomes necessary to maintain adequate pressure and flow.
RPM Range and Operating Conditions
The engine’s typical operating RPM range significantly influences pump selection. If your engine isn’t built to rev beyond 5,500 RPM, you probably do not need a high volume oil pump. Most street engines spend the majority of their time at moderate RPM where standard pumps provide adequate lubrication.
Racing applications present different requirements. There’s an old racing rule of thumb that still applies here: Approximately 10 psi of oil pressure is needed for every 1,000 rpm. An engine that regularly operates at 7,000 RPM would require approximately 70 psi of oil pressure, which may necessitate a high-volume or high-pressure pump to maintain adequate lubrication.
The duration of high-RPM operation also matters. Drag racing engines that see brief bursts of high RPM have different requirements than road racing or circle track engines that sustain high RPM for extended periods. The only time a HV pump is a good way to go is if your running excessive RPM’s for an extended period of time or your engine was built clearenced fairly loose.
Additional Oil System Components
When additional components are added to the oiling system, oil volume requirements increase. Switching to a high volume oil pump is necessary if an engine builder plans to use larger bearing clearances or is expanding the amount of oil contained in the lubrication system (adding remote filters or an oil cooler). Each additional component adds restriction and volume to the system, requiring more pump capacity to maintain adequate flow and pressure.
However, it’s important to understand that not all additions require increased pump volume. A remote filter and/or Accusump does not change any volume demands on the oil system. Nor do they bleed off pressure. These components simply relocate or store oil rather than consuming it, so they don’t necessarily require a high-volume pump.
Stock vs. High-Volume: Making the Decision
For most street engines with proper clearances, a standard pump is the appropriate choice. If there’s no need to go with a high volume and/or high pressure pump, don’t. Most engines will do just fine with a stock flow pump provided the engine’s bearing clearances are within normal specifications and not too loose. This approach minimizes parasitic losses while providing adequate lubrication.
The myth that high-volume pumps will drain oil pans has been thoroughly debunked. A high-volume pump WILL NOT suck the pan dry. Clogged oil drain-back holes and poor oil control will. Windage trays and crank scrapers help to prevent this. Proper oil pan design with adequate baffling is more important than pump selection for preventing oil starvation.
Similarly, concerns about high oil pressure washing out bearings are unfounded. High oil pressure WILL NOT “wash out” your bearings. Excessive heat from low oil flow will overheat and destroy your bearings. This is usually caused by bearing clearances that are too tight. The real enemy of bearing longevity is inadequate flow and excessive heat, not high pressure within reasonable limits.
Understanding Oil Pressure vs. Oil Flow
One of the most critical concepts in oil system design is the distinction between pressure and flow. Oil pressure is to be understood as the resistance in the engine which the oil overcomes to establish a certain flow rate. The most important criterion for good oil lubrication is optimal oil flow and not oil pressure. This fundamental principle often gets overlooked in discussions about oil pumps.
Pressure is simply a measurement of resistance to flow. Oil pressure is the measure of resistance to flow. When bearing clearances are tight, resistance increases and pressure rises. When clearances are loose, resistance decreases and pressure drops—but flow may actually increase through those looser clearances.
The ideal scenario is high flow with moderate pressure. A fast flow rate with lower oil pressure will result in minimal wear and optimal cooling. This combination ensures that fresh, cool oil constantly circulates through bearings, carrying away heat and contaminants while maintaining the protective oil film.
Conversely, high pressure with low flow creates problems. A low flow rate with high pressure will result in a less efficient lubrication and cooling and therefore more wear on the engine. Too high an oil pressure can result in failure of seals and leaking of oil and should therefore be considered as an indication of poor flow. This situation often indicates restrictions in the oil system or inappropriate oil viscosity for the bearing clearances.
Bearing Clearances and Oil Viscosity Selection
Bearing clearances and oil viscosity work together to determine oil system requirements. Reducing the oil clearance between the rod and main bearings and the crankshaft has a number of advantages. A smaller gap spreads the load over a wider area of the bearing surface and distributes pressure more uniformly across the bearing. Tighter clearances also reduce the volume of oil required to maintain the protective film.
Modern engine building trends favor tighter clearances with thinner oils. Tight bearing clearances and relatively thin synthetic multi-viscosity motor oils work well in many performance applications from NASCAR and circle track racing to drag racing. Keep in mind, however, that most of these engines are purpose-built engines that are machined with exacting tolerances. This approach reduces parasitic losses and can free up horsepower.
However, looser clearances require different approaches. In the case of this typical 0.0025-inch clearance, conventional wisdom calls for a 10w-30 or 10w-40 oil. If the clearances are larger – around 0.003-inch or more for larger journal engines such as a 455 Oldsmobile, then a thicker oil such as a 20w-50 is generally used to maintain the proper lubrication barrier. The thicker oil is necessary to maintain adequate film thickness in the larger clearances.
Oil temperature also plays a crucial role in viscosity selection. An engine with an iron block with 0.0025-inch main bearing clearances that sees oil temperature in excess of 220 degrees would be best served using a 10w-40 or 15w-40 viscosity oil. Higher temperatures reduce oil viscosity, so hotter-running engines may require thicker oils to maintain adequate protection.
Parasitic Power Losses and Performance Considerations
Every component in an engine that moves consumes power, and the oil pump is no exception. The power required to drive a high-volume pump is measurably higher than a standard pump. The only down side is a HV oil pump uses about 1-2 more horsepower to run than a stock pump at 5k rpms. For most street applications, this loss is negligible, but for maximum performance builds, every horsepower counts.
Professional racing teams often run minimal oil pressure to reduce parasitic losses. Most if not all NASCAR race teams today run very low oil pressure (around 5 PSI per 1000 RPM) and use stock volume oil pumps to minimize parasitic horsepower losses to the oil pump. But they are also running thin 0W-20 synthetic racing oil and very tight bearing clearances (.001 inches or less). This approach requires precision machining and careful monitoring but maximizes available power.
The trade-off between protection and power must be carefully considered. A smaller gap also decreases the volume of oil that has to flow into the bearing to maintain the oil film between the bearing and shaft. This also reduces the amount of oil pressure the engine needs, so some extra horsepower is gained by reducing the load on the oil pump. For street engines where longevity matters more than peak power, erring on the side of more lubrication is typically the wiser choice.
Common Myths About High-Volume Oil Pumps
Several persistent myths surround high-volume oil pumps that deserve clarification. The first is that they will drain the oil pan dry. If a pan is pumped dry, it is because the holes that drain oil back to the pan are plugged. Proper oil return passages and adequate pan capacity are the real solutions to oil starvation, not avoiding high-volume pumps.
Another myth suggests that high-volume pumps will wear out distributor gears. It will not wear out distributor gears. The load on the gear is directly related to the resistance to flow. Oil pressure is the measure of resistance to flow. While it’s true that high-volume pumps create more load, properly designed drive systems can handle this load without premature failure.
The concern about oil foaming is also largely unfounded. It will not cause foaming of the oil. With any oil pump, the excess oil not needed by the engine is recirculated within the pump. Foaming is more commonly caused by excessive oil levels, inadequate windage control, or oil returning to the pan without proper deaeration.
Perhaps the most important myth to dispel is that high-volume pumps are problematic when installed in engines that don’t need them. High volume pumps can be a big advantage if used where needed. If installed in an engine that does not need the additional volume, they will not create a problem. The additional flow will be recirculated within the pump. The relief valve ensures that excess pressure is bypassed, preventing damage while still providing the benefits of increased flow capacity when needed.
Practical Recommendations for Different Applications
Street Engines
For typical street engines with stock or near-stock specifications, a standard oil pump is almost always the correct choice. These engines operate primarily at moderate RPM, have tight bearing clearances, and don’t require the additional flow capacity of a high-volume pump. The standard pump provides adequate lubrication while minimizing parasitic losses and complexity.
If a street engine has accumulated significant mileage and bearing clearances have increased, a high-volume pump can temporarily restore acceptable oil pressure. However, this is a band-aid solution. Some people may install a high-volume pump in a high-mileage engine in an attempt to restore normal oil pressure. But, the only real cure for low oil pressure is to replace worn bearings and restore normal clearances. Proper engine rebuilding is the correct long-term solution.
Street/Strip Performance Engines
Engines that see occasional track use but primarily serve as street drivers occupy a middle ground. If bearing clearances are kept within reasonable limits (0.0025 to 0.003 inches) and the engine doesn’t regularly exceed 6,000 RPM, a standard pump typically suffices. However, if clearances are opened up for performance or if the engine regularly sees high RPM, a high-volume pump provides valuable insurance against oil starvation.
For these applications, proper oil pan design becomes critical. Adequate capacity, trap door baffles, and windage control features help ensure consistent oil supply to the pump pickup during acceleration, braking, and cornering. These features are often more important than pump selection for preventing oil starvation in street/strip applications.
Racing Applications
Dedicated racing engines often benefit from high-volume pumps, particularly when bearing clearances are opened up for performance. In the realm of ‘standard’ performance or racing engines of today, I use high volume pumps with standard pressure levels. This is mainly with larger bearing clearances that need the volume more than the pressure to ensure adequate lubrication. Additional volume is needed to occupy those increased clearances, not pressure.
However, even in racing applications, the decision isn’t automatic. Short-duration events like drag racing may not require high-volume pumps if clearances are kept tight and oil temperature is controlled. Endurance racing or circle track applications where engines sustain high RPM for extended periods benefit more significantly from increased oil flow capacity.
The key is matching all components of the oiling system—pump capacity, bearing clearances, oil viscosity, pan design, and cooling capacity—to the specific demands of the application. No single component can compensate for deficiencies in the overall system design.
Final Considerations and Best Practices
When evaluating whether to install a high-volume oil pump, start by honestly assessing your engine’s actual needs rather than following generic recommendations. Consider bearing clearances, typical operating RPM, duration of high-RPM operation, oil system modifications, and intended use. If your engine has tight clearances, operates primarily at moderate RPM, and serves as a street driver, a standard pump is almost certainly adequate.
If you do install a high-volume pump, ensure that supporting components are adequate. Verify that your oil pan has sufficient capacity and proper baffling. Consider whether your pump drive system can handle the increased load, particularly on engines known for distributor gear failures. Monitor oil pressure and temperature carefully during initial operation to ensure the system is functioning as intended.
Remember that oil pressure alone doesn’t tell the complete story. A gauge showing high pressure doesn’t necessarily mean adequate lubrication if flow is restricted. Conversely, moderate pressure with good flow provides better protection than high pressure with inadequate flow. Focus on ensuring adequate flow to all engine components rather than simply maximizing pressure readings.
Regular oil analysis can provide valuable insights into whether your oiling system is adequate. Bearing wear metals, oil temperature, and viscosity breakdown all indicate how well your lubrication system is performing. This data-driven approach is far more reliable than guessing based on pressure gauge readings alone.
Ultimately, the decision to use a high-volume oil pump should be based on specific engine requirements rather than assumptions or myths. When properly matched to engine specifications and operating conditions, high-volume pumps provide valuable benefits. When installed unnecessarily, they add cost and complexity without meaningful advantages. Understanding your engine’s actual needs is the key to making the right choice.
For additional technical information on engine lubrication systems, consult resources from Engine Builder Magazine, OnAllCylinders, and EngineLabs. These publications offer detailed technical articles from industry professionals and engine builders with decades of experience in optimizing engine oiling systems for various applications.