Pumped Up

Lubrication Systems

Bob Mehlhoff Apr 9, 2005 0 Comment(s)

At 3,000 rpm, the pistons inside your engine are moving up and down violently, the crankshaft is spinning swiftly, and the rocker arms are rapidly doing the two-step with each respective valve. But whether your engine is just idling in drive or at full-throttle, it takes a good lubrication system to keep everything from turning into molten metal. To prevent this unsavory transformation, oil is directed to all of the metal contacting surfaces by a full-pressure lubrication system comprised of an oil pan, an oil pump, several quarts of oil, and a series of passages inside your engine. To learn more about how this stuff works, this month's segment is devoted to the lubrication system of a typical Chevy V-8.

A stock Chevrolet V-8 engine uses a wet-sump system (oil reservoir located directly below the crankshaft) with internal passages within the cylinder block, crankshaft, and openings in the cylinder heads. A 1/2-inch diameter oil pump inlet on small-blocks (5/8-inch diameter on big-blocks) with an ample suction screen submerged in engine oil provides free-flowing oil to the pump, which is driven by the camshaft. The oil that is supplied to the pump travels through a full-flow oil filter into a 1/2-inch main gallery on a small-block (9/16-inch on a big-block) that is located above the camshaft. From there, the lube travels through a hole to a groove near the rear side of the rear cam bearing ('57-and-later V-8s) and is where the lifters and rear main are oiled. Additionally, all four front cam bearings have grooves that pass to each particular main bearing. Through small holes in the upper main bearings, oil passes down into the crankshafts main journals where it travels to the rod journals.

While all of this is occurring, the crankshaft is spinning and each connecting rod is throwing oil onto the respective cylinders to lube the moving pistons and rings and help seal combustion. At the top of the engine, oil has traveled from each lifter and up through the hollow pushrods, over the rocker arms, and down onto the springs and valve stems where it helps to lube the valve stems as they move in the valve guides. To keep the pressure from getting too high at the oil pump, a relief valve circulates the oil back to the inlet side of the pump when pressure surpasses the relief spring's limit.

High-performance engines place increased bearing loads on the oiling system (especially during higher rpm), and if it's not up to the task, it can cause very premature engine failure. To combat this, most aftermarket high-performance pumps provide a 20-30 percent increase in both volume and pressure. For most applications, you'll want a good pump that delivers in the neighborhood of 55-65 psi or about 10 psi per every 1,000 rpm; anything more may just add air into the system or labor the engine with the task of turning an oil pump that makes excessive pressure. If you doubt that an oil pump takes power to turn, watch what happens to a drill motor during the initial phase of oil pump priming.

Most aftermarket pumps come with a new pickup installed and brazed into position. If yours does not, you should braze the pickup into the pump body, positioned about 1/4-inch (0.250-inch) above the bottom of the pan. Before brazing it to the pump cover, remove the pin, spring, and relief piston from the cover so that the heat won't damage them. Put the pump securely in a soft-jawed vise and tap the pickup into the oil pump with a homemade tool or one from a specialty tool company. To measure the pickup-to- pan clearance, place a small piece of clay between the pickup and bottom of the pan and install the oil pan gasket in a mock-up (without adding sealant).

But before you install a new oil pump onto the engine, it's always a good idea to double-check the end clearance of the pump gears beforehand. For most small- and big-block Chevys, the pump gear's end clearance should be very close to 0.0025-inch, but it's always best to first check with the pump manufacturer for the spec. To check this dimension, disassemble the pump and de-burr both gears with a small file. Then, reinstall both gears and measure the endplay (from the top of the gears to the top of the pump housing) using a depth micrometer or a feeler gauge. If you install a pump with a measurement that exceeds the 0.0025-inch spec, then the pump will not prime as easily and/or perform as well. If the endplay is greater than this, it can be corrected by sanding the pump body with a piece of solvent-wet 220 wet/dry sandpaper placed on a hard and very flat surface, such as a thick piece of glass. To correct clearance that measures too small, sand the gears on the top end in the same manner as the pump body. In either case, remember to wash everything in solvent and then blow-dry it (rags will leave lint) before reassembly.

To install the pump on the rear main cap, first be certain that the hole in the pump aligns with the hole in the main cap. This may require chamfering the holes so that they line up with each other.

Supply and Demand
Look inside of a stock or high-performance pan and you'll see baffles there to keep the oil pickup submerged during cornering, accelerating, or stopping. For high-performance pans, the baffling is typically far more elaborate and designed to better withstand the forces of extreme-duty operation. Critical to a good oil pan's design is also how well it allows gravity drain-back into the sump.

For many high-performance applications, the size of the sump may be larger than stock. For most street-driven cars, chassis and ground clearance requirements dictate the depth (and width) of the oil pan's sump area, so for many applications, wide sump pans are available.

At engine speeds above 6,000 rpm, the moving oil can whip the crankshaft and cost power. This phenomenon is called windage and is minimized by installing either a windage tray or a semi-circular screen to move the oil away from the spinning crankshaft without splashing back on the throws.

ConclusionBuilding the best oiling system for your engine depends on planning, budgeting, and how you'll use your vehicle. If you're simply building for moderate street and limited track use, there are many high-performance oil pumps and oil pans that will increase volume and pressure without destroying your budget. For very high-performance use, there are a multitude of oil pans, pumps, windage trays, and hardware to almost eliminate the possibility of encountering an oiling problem. The key is choosing the right parts, installing them correctly, and operating the engine the way it was designed. CHP

11

This Moroso high-performance oil pump has many features designed to provide a consistent flow of oil to the engine. The special anti-cavitation slots prevent the formation of oil foaming. The unique feeder grooves, enlarged bypass area, as well as the anti-cavitation slots, work to bleed oil back to the inlet side of the pump. This all adds up to a pump that provides a smooth and consistent oil flow and places an even load on the distributor shaft to help eliminate spark scatter at high rpm.

From the oil pump, oil travels through the filter and into the block. After the initial 20 to 30 minute run-in of a new engine and camshaft, it's a good idea to drain the oil (with the engine still warm) and install new oil and a new oil filter. Neophyte engines produce a lot of small and sometimes microscopic debris. The adapter and spin-on filter, which began appearing on '68-and-later Chevy V-8s, is available from your GM dealer or Mr. Gasket. The Mr. Gasket adapter sells for about $18 (PN 1272).

A cutaway shot of a new GM Vortec engine shows an oil filter from the inside out, as well as the internal path that the engine lube travels to and from the filter from the oil pan. This is called a wet-sump system because it carries the oil in a pan directly below the crankshaft and is what 99.99 percent of all modern production cars use. As a side note, some dedicated race engines (and the new '06 Corvette LS7/Z06 427) use a dry-sump system where oil is stored in a remote tank.

This new Moroso CNC Billet racing oil pump (PN 22163) (a) provides closer internal tolerances to ensure very precise performance and pressure. Notice how large the inlet area is compared to the street style pump (b).

The oil pump gears add more flow...

...require a taller oil pump housing (arrows).

The stock oil pump shaft may work fine for a production-type low-pressure pump, but if you're adding a pump with higher pressure, replace the original shaft with a quality steel shaft (left) to withstand the added pressure (available from Milodon and Moroso).

The pickup provides the inlet for oil into the pump, and should be set 0.250-inch above the bottom of the pan (measured with a test gasket in place). Use a small piece of hobby shop clay to measure yours. The pickup shown (above) features a strap to secure it to the pump.

This small-block is fitted with a windage screen and an aftermarket pickup designed to fit a special oil pan. At high rpm, a windage tray will provide extra horsepower because it keeps the crank throws from hitting the lube.

Special studs, like these from ARP, mount the windage tray into position.

The stamped steel screen on the bottom of the pickup prevents large debris from entering the pump and inhibits oil from leaving the inlet tube.

At high-rpm, about three quarts of oil are on top of the engine (out of the pan), and there is always close to a quart in the filter, leaving one more quart in the pan in a typical five-quart system (right). A vehicle used for high-performance (high-rpm operation) driving should have a larger oil pan. For most drag-racing use, a deep sump pan works well because it adds capacity without increasing the area around the bottom of the pan as a wide-sump pan will (left); the wide sump spreads the area out around the pickup and more oil is required to keep the pickup submerged. Granted, for many street and road race applications a wide sump pan is the best high-performance choice because of ground clearance and steering linkage issues.

If you need an oil pan for a unique installation, Dooley Enterprises custom makes some high-performance pans to order. Although largely for marine use, they also offer pans like this one for a '66 Chevy II that is receiving a GM Ram Jet 350 crate motor.

New GM oil pans, such as this one used on the production Vortec 2800 I4, are cast from aluminum and feature special walls to contain and drain-back the oil. Cast-aluminum pans are also more rigid, especially along the gasket surface and are not as prone to leaking.

This close-up shot of a pickup installed in the pump cover shows what a brazed-in pickup tube should look like. Just remember to remove the relief spring before heating up the pump for welding or the spring may weaken causing lower oil pressure.

This high-performance pump has a nice wide opening, which allows oil to travel freely through the rear main cap. If the cap does not have an accompanying hole to match, some chamfering may be needed.

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