The oil is the literal lifeblood of your engine, and the oil pump is its heart. Adequate lubrication is absolutely essential, and making sure that we’ve got plenty of pressure and flow to all the right places is what makes engines live and last. When it comes to oil pumps, the best choice for your particular engine depends upon several critical factors.
First and foremost, the purpose of the engine is an essential factor that must be considered. Is this a racing engine, or a street engine? If it’s a race engine, will it be for drag racing, road racing, autocross, or circle track use? If it’s a street engine, will it be used daily, or will it be a weekend toy that might see occasional track use?
Basic Oil Pump Upgrades
The basic bolt-on, out-of-the-box oil pump offerings available to most hot-rodders are pretty limited, but oil pumps from companies like Melling and Moroso have been proven to be pretty effective and reliable options. Most builds will use a factory-style internal pump with an OEM wet-sump oiling system, or you can get really involved and add an aftermarket external (typically belt-driven) pump in either a wet- or dry-sump setup. The overwhelming majority of performance cars (and trucks) rely on upgraded or modified versions of what the factory shipped the engine with, so we’ll start our discussion there.
Oil pressure is defined by two primary factors: pressure and flow. High-performance engines are generally given more of each, with higher pressure and a greater amount of flow. Basically, the flow rate is defined by the quantity of oil the pump is capable of moving. Increasing the physical size of the inlet, outlet, and the height of the spur gears (in a traditional gear pump) or rotors (in a gerotor design) will allow the pump to move a larger quantity of oil.
The pump’s output pressure is limited by a spring. Naturally, spring tension is adjustable, and pressure can be adjusted by either adjusting the tension on the existing spring, or changing the spring altogether. The pump pushes pressure against the spring until a bypass valve is pushed open, which will not allow pressure to increase any further. Still, if the size of the bypass valve becomes the limitation, the pressure can increase a bit more. This happens because the pump keeps moving more lubricant with gains in engine RPM. Hot-rodders and racers have dabbled with these adjustments with varying degrees of success over the years.
The factory engineers spend a lot of time designing and refining the oiling system. Its job is huge, as it must provide adequate lubrication to the engine in all situations. These include a wide range of temperatures (from way below zero to way over 100-degrees Fahrenheit) and an incredible amount of demands. The factory oil pumps do a great job, for the most part. It’s only when we demand so much more from our engines in racing situations that we are forced to look at upgrading flow rate, pressure level, or both.
Additionally, we need to consider the level of development our engine had when we consider upgrades. A vintage Nailhead or Stovebolt Six engine will require more oiling upgrades than a new LT or Coyote. Any traditional Pontiac, Olds, or Buick V8 builder will have a long list of oiling system upgrades they do for all their high-performance engine builds, and many for the stock rebuilds too. Blueprinting the pump to ensure all the clearances are correct is only the beginning, and careful porting of the pump mount, upgrading the mounting bolt(s), and carefully enlarging the drainback passageways are all part of the plan when it comes to prepping a vintage engine design for increased power, RPM, and endurance.
It is possible for a pump to be over-modified and pump too much oil at too high of a pressure. “When it comes to increasing pressure and/or flow, it really depends upon the engine, its intended use, what kind of clearances I gave it, and what kind of oil system I am using. Every high performance engine is different, also the type and viscosity of oil make a difference,” says John Beck of Pro Machine and John Beck Racing Engines. “90-percent of all engines do not need more than 50 or 60 pounds of oil pressure. Even most drag race engines under 800 horsepower don’t need much more than 60 to 70 pounds, maximum.”
Mike LeFevers of MiTech Racing Engine agrees, saying, “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.” To that end, if you increase bearing clearances, and just increase oil pressure and not volume, the elevated oil pressures can actually lead to oil being pushed past the critical areas requiring lubrication, without having time to do it’s job. Additional volume is needed to occupy those increased clearances, not pressure.
Another concern for running an oil pump with too much output, is actually running the oil pan dry. “If the pan sump is being drained at a higher rate than it can drain back to the pan, the pump can run itself dry. At the Bonneville salt flats, we have a unique problem, since most of the time we are at full throttle for five solid miles, and too big of an oil pump (moving too much volume) will certainly empty out the oil pan before the end of the run,” Beck explains. “Everything has to be engineered to suit it’s specific purpose.”
It used to be more of a concern before baffled, deep sump oil pans were a regular part of racing — that’s actually the reason they were developed. Similarly, road race wet-sump pans typically have large kick-outs on each side that hold a larger quantity of oil. These are similarly protected by trap doors, like the deep sumps in the drag race pans. These tricks exist to ensure the pump pickup always has plenty of oil feeding into the pump, regardless of what the car is doing.
Types of Wet-Sump Pumps
The newer GM LS, Ford Modular, and Chrysler Hemi V8 all use front-mount gerotor design oil pumps, and that’s no accident. The gerotor design simply has better flow characteristics than the traditional old school oil pumps that use twin, side-by-side spur gears. The new-style gerotor pump drive directly off the crank, versus the older style pumps that drove off the cam, usually in line with the distributor.
Remember, the cam runs at half the speed of the crank, so the new-school pumps spin twice as fast. The direct-drive design also means there’s no oil pump shaft used, and anyone who’s ever broken or twisted an oil pump drive would tell you that’s a great improvement in the evolution of the V8.
This isn’t to say that the new stuff is without issue, or that the vintage stuff was horribly flawed. Certainly, vintage engines of all makes performed some amazing tasks over the years. With the proper upgrades and well-engineered mods, adequate oil flow has allowed the classic designs to spin at high-RPM for extended periods and accomplish great things.
This is still the case and if you are dedicated to a traditional make or style of classic engine, know that the homework has been done, and is continuing to be done to help you achieve modern lubrication needs with classic engines. Some engines need more pressure, others need more volume, and most need the drainback pathways improved and a better pickup design.
Mounting the pump to the crank, as the new engines do, isn’t a cure-all… but it’s close. The longer pickup tube means it takes a tiny bit longer to get pressure to the engine on a cold start, but obviously, this hasn’t been a deal-breaker for fans of late-model power (or the manufacturers who warranty these new engines in all the new cars and trucks they sell).
In extreme high-performance applications, where higher RPM levels translate to higher demands on the crank-mounted pump, the mounting surface to the cover can be overtaxed. The addition of a gasket (most stock pumps don’t use them anymore) and improved mounting hardware, along with a stiffer front cover can eliminate any potential issues.
And while gerotor pumps mounted to the crankshaft are far less susceptible to cavitation issues than more traditional spur-type gears (they have to be as they spin at crankshaft speed) they are not immune to the problem. When cavitation issues do occur in a crank-driven gerotor application, there exists a last line of defense, to keep a wet sump oiling system, and that’s the remote-mounted wet sump pump.
Often mounted in a very similar manner to a dry sump oil pump, a remote-mount — or “external” — wet sump oil pump has the advantage in extremely high-RPM applications of offering a gear reduction to operate the pump at a fraction of the crankshaft speed (alleviating RPM-based cavitation concerns), but still providing very-increased oiling capabilities, at the cost of, well, cost and system complexity.
For most of us, upgrading to an improved aftermarket pump and matching pickup should be all that’s needed. Properly measuring and adjusting the clearance between the bottom of the pump pickup and the pan is also critical, since too much clearance isn’t good (air could be drawn into the pump if the pan is low on oil) and too little isn’t good either (the pickup can’t be too close to the bottom of the pan, as its capability the draw oil in will be restricted). Properly setting this and checking it during assembly (typically with modeling clay under the pump pickup, and checking with the pan gasket in place) is the norm. Once adjusted and properly clearanced, the pump pickup tube can be welded or epoxied permanently into position.
There are also high-performance coatings that have been proven to assist the oil pump in doing its job. These graphite coatings can be applied to the moving parts inside the pump and also to the inside of the pump housing to assist the pump in doing its job. The use of coatings inside the pump minimizes the friction inside the pump and limits the effect heat will have on the critical clearances within the pumps as well.
Moving to a Dry County
To this point, we’ve only been discussing street-based, factory systems that are directly related to what our cars shipped with. If we were to define this from an engineering perspective, we’d call them wet-sump systems. The sump is defined as where the oil is stored when it’s not circulating throughout the engine, so in our case, it’s basically the oil pan. The pump pickup lives in the bottom of the pan, so it’s a considered a wet-sump. The alternative to this is a dry-sump, which is what most full-race vehicles rely on (typically, unless specifically disallowed in the rules).
A dry-sump, as the name implies, does not store the oil in the pan. Rather, it’s stored in a remote tank. The tank supplies oil to the pump, which is typically an external, belt-driven component. That same pump scavenges oil that drains to the pan, which is much smaller and designed to collect and direct the oil to the pump so it can be returned to the tank. It sounds a lot more complicated, and in many ways it is. It does rely on many more components, and a lot more plumbing to connect everything together. There are enough benefits to justify all of this, of course, and the essential need for a constant supply of lubricant to the engine (or specifically, to the pump) is chief among them.
Among the benefits of the dry-sump, the lack of air bubbles in the oil (aeration) ranks really high too. When the oil is returned to the tank, the air that has been stirred into it is allowed to separate. The oil being drawn back into the engine is bubble-free, which is ideal. If bubbles are drawn into the pump, it can cavitate, which means air is mixed in with the oil and during cavitation the pump is not moving near as much oil as it should.
As a result, pressure won’t be maintained at the designated level either. This is because air can compress, while fluid can’t. When air passes through the pump, it occupies the space that should be full of oil and doesn’t maintain the same level of pressure. These are both bad things, and far more mitigated in a dry-sump design than a wet-sump setup.
Making Wet and Dry Work
If a wet-sump setup were to be used in something like an off-road vehicle, consider the difficulty the pan would have controlling the oil inside of it and delivering it to the pump pickup, while bouncing around in three different axes. The effect is similar with hardcore autocross and dedicated road racing cars, with heavy G-loads in the turns and long corners being taken at high speeds.
Similarly, in drag cars, the G-forces pushing the oil to the rear of the pan during an aggressive launch (especially when the front wheels are up in the air) make it really hard to keep oil contained at the pickup, unless the pan is specifically designed to hold additional oil and hold it for the pickup.
In full-race applications, particularly in cornering cars, trap-door-equipped wet-sump pans exist and they do make a big difference, but dry-sump setups have proven to be superior. Due to the remote tank design and expanded use of plumbing, dry-sump designs typically hold a lot more oil than traditional wet-sumps, and having more oil capacity in the system means there’s more available and it’s easier to cool. Speaking of cooling, most dry-sump designs have an oil cooler included. Since so much oil is being moved through the plumbing, integrating a nice oil cooler (or two) into the design isn’t too difficult.
The dry-sump pumps are typically engineered with a series of scavenge and pressure sections. How many of each type depends on the application, but they are typically identical, meaning that all of the scavenge sections are the same, and all of the pressure sections are the same. Once the appropriate amount of sections are assembled together in sandwich fashion, the pump is mounted to the engine and a spindle is added (typically with a toothed Gilmer belt drive) and the dry-sump oil pump is crank-driven. The scavenge sections draw from the base of the pan, and the pressure sections feed directly into the block, typically into the main galley (for the main bearings) and the cam galley (for the cam and valvetrain).
Taking it to the Streets
While the exotic dry-sump setups are typically considered overkill for any street application, automotive evolution is constant and high-end factory Z06 Corvettes have had them since 2006. The Z06 setup isn’t as extreme as a dedicated aftermarket racing design, but it doesn’t have to be. It’s certainly an effective design when compared to comparable wet-sump designs from the same era.
As a result of the Z06 dry-sump, the factory parts are readily available to upgrade your hot rod (or off-road truck) to take advantage of the design. It’s worth looking into if you’re an autocross or Pro Touring enthusiast who is looking to toss their LS-powered ride around pretty hard on a regular basis.
For the rest of us, a carefully-engineered upgrade of factory-style components has proven adequate for decades. These include a well-engineered pump, as discussed, which is supported by a properly-executed and mounted pickup and pan. Upgrading to a premium filter assembly (or even a remote dual-filter arrangement) can only help. The same can be said for a well-designed oil cooler, if necessary.
So, do we upgrade for increased pressure, increased volume, or both? Experience over the years has proven that increased volume is what street engines benefit the most from. Moving a higher volume of oil at the same pressure levels is more beneficial than cranking up the pressure to sky-high numbers. Higher pressure requires much more power to create, and that steals precious horsepower right from the tires.
Generally speaking, for most street and race applications, you don’t want it to drop below 20 psi at any point, but it doesn’t need to go much higher than 45 psi either. A very well-known Pro Stock engine builder told me in confidence that he limited the oil pressure on his 500ci carbureted race engines to 35 psi, max.
Granted — they only had to run hard for six seconds, but much of that was done at over 7,500 rpm too. I am confident there was a large volume of oil being moved through that engine, but I believe him that it didn’t go past 35 psi. So, why would your street car need 60 psi of oil pressure when the engine is at normal operating temperature? It wouldn’t.
Focus your efforts on efficient oil control. Make sure it gets picked up easily, filtered completely, pumped without restriction to all the critical parts of your engine, and that it can drain back to the sump easily. Ensure it doesn’t get too hot, and that there is sufficient quantity in your system to pump at high volume without running the sump dry. Check it often, and use a good synthetic oil in engines you care about.
As we stated at the beginning, oil is the lifeblood of your high-performance engine, and the oil pump is the heart. Taking the time to ensure that you have an oiling system capable of moving the proper quantity of oil at the correct pressure and temperature is a relatively cheap insurance policy. If you know your engine can provide enough oil and you allow it drain back at sufficient rate to keep up with the RPM and g-force loads you’re pushing it through, you should be all set. Don’t hesitate to check with others doing similar work — you might be surprised to learn the effort and engineering that’s been put into the oiling system that you can’t see or hear from the outside. It’s worth it!