About the only attention most people give to engine oiling is a fresh filter and four or five new quarts of 10W-40 every couple thousand miles. For serious engine builders, however, the intricacies of an engine's lubrication system are something to puzzle over. We scheme to make it work better and take less of a toll on the output at the end of the crank. The masses may think we're nuts, but engine oiling is both a matter of survival and making maximum power.
We've often heard that the right oil pan and accessories like windage trays and crank scrapers can be worth considerable power in certain applications, and we recently experienced this firsthand during a dyno-test that wasn't going our way. A previously baselined engine was suddenly down about 20 hp after sitting on the shelf for a few weeks. After some head scratching, our sharp-eyed dyno operator drained about a quart and a half of oil out of the pan, and the power came back. It turns out we poured one too many quarts into our stock 5-quart pan. That's just one example of power being robbed by an oiling system.
Gearheads like us think about lubrication in terms of windage, control, and delivery, while those outside our world think about earning a free car wash coupon with an oil change. The lubrication concerns covered here are for guys like us; let the masses read about miracle diets and Jennifer Aniston.
What it is: Oil pumpWhat it does: The heart of the lubrication system, the oil pump delivers oil to the galleries to supply the engine's internals with precious lubricant
Features: Unless you have a splash-lubed '20s Marmon, you need an oil pump. But what should you look for? The most commonly confused aspect of pump performance is the relationship between volume and pressure. These may be separate attributes, but they are intrinsically linked. To maintain a given oil pressure, a given volume of oil flow is required. How much flow is necessary depends on the engine's internal clearances, or in a sense, how quickly the pressurized lube is fed in versus how quickly it bleeds past the engine's internals. Loose clearances represent a greater pressure leak and result in a lower oil pressure. Increased pump capacity (volume) will maintain a greater pressure level under the same conditions. The pressure will also vary according to the viscosity of the oil-the thicker the viscosity, the higher the flow resistance and the slower it will bleed through the system.
A properly matched pump normally has more volumetric capacity than the engine needs, and it will therefore build excessive pressure if unregulated. The excess capacity of the pump is normally bypassed via a built-in spring-loaded regulator assembly. The pressure level is controlled by bleeding off a portion of the excess volume either back to the feed side of the pump or to the sump. Under some circumstances, excess pressure can be produced if the bypass circuit has insufficient flow capacity. Often this is the case with a cold engine running thick, heavy oil. The cold oil can't be bypassed fast enough to keep the pressure down, particularly as oil pump speed and output volume increase at high rpm.
Comments: Production oil pumps are primarily of two designs-the plain spur-gear pumps common to many GM engines including big- and small-block Chevys, and the gerotor pumps found in Mopar engines among others. Gerotor pumps are superior in capacity, efficiency, and stability. Spur-gear pumps are adequate for most performance applications, but there's a high-frequency pulsation or chatter inherent in their design that transfers via the oil pump drive to the distributor and camshaft. Racing mods include relieving the discharge port to lessen the change in discharge-port area open to flow as the pump's driven gear rotates. Anti-chatter grooves are often cut into the pump body and cover to reduce the pulsating effect. Racing pumps are available that incorporate some of these design considerations.