In most applications, small-block Chevy oiling systems are probably the simplest and most reliable arrangement ever offered. While oiling problems may still be encountered, they are almost always the result of some other problem. Common sense preparation is all that’s required for basic high-performance small-blocks.
Small-blocks require very clean oil and regular filter changes. A steady, nonfluctuating oil supply between 150 and 270 degrees at 60 to 80 psi is recommended. This recommendation is intended primarily for racing applications and is probably a little excessive for a street-driven motor. Most street engines operate just fine with 35–50 psi of hot-oil pressure. Some drag racers are comfortable running 30–40 psi at 8,500 rpm. We don’t necessarily recommend this, but it’s a good indication of how well the small-block oils. Modern competition oiling systems often include drysump scavenging and a variety of minor refinements, many of which have been designed into the recent Bow Tie blocks.
This Tech Tip is From the Full Book “SMALL-BLOCK CHEVY PERFORMANCE: 1955-1996“. For a comprehensive guide on this entire subject you can visit this link:
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Perhaps the best recommendation for a street engine is moderation. Keep oiling system modifications to a minimum. Your main concern should be with keeping the pickup covered with oil at all times. There are basic blueprint specs to be followed and we will offer some tips regarding oil temperature and oil control. But first we need to take an overall look at the small-block’s oil delivery system to get a feel for just how it lubricates every internal moving part.
The main oil gallery runs parallel to the camshaft and directly above it. The lifter galleries run directly through the lifter bores on either side of the main gallery. In the bottom end, each pair of cylinders is separated by a main bulkhead with a vertical oiling hole connecting the main gallery to the camshaft journals and then to the main bearing journals. Although the engine oils the cam journals “before” it oils the main bearings, this has not been found to have any adverse side effects in street and moderate high-performance applications. Some recent Bow Tie blocks are designed to provide “priority main” oiling that feeds oil to the main bearings directly from the oil gallery.
These blocks also feature a front inlet to themain oil gallery to simplify dry sump plumbing. Most racing mechanics favor restricting the valvetrain oiling so thatmore oil is available for the lower end, but this should be considered a racingmodification only. Solid or roller lifters and roller rocker arms that don’t require a large amount of oilmust be usedwhen oil flowto the valvetrain is limited.
The oil pump is attached directly to the rear main cap. A passage intersecting the main feed from the pump provides direct oiling to the rear main bearing. Oil from the pump continues its flow through the oil filter and up to the center main gallery where it oils the cam and main journals and fills the lifter galleries. Oil in the lifter galleries lubricates the lifters and is fed up the pushrods to the rocker arms and valvestems. Upper engine oil returns via holes in the valley that drain oil back into the sump. This system works fine for street applications, but at high speeds, power is lost when oil draining back contacts the spinning crankshaft. The small-block is often modified to redirect return oil to the front or rear of the block, where large drain-back passages route oil directly to the sump.
When you look at factory oil-flow diagrams, you also notice that the oiling holes in the crankshaft lead the TDC position by 60 degrees so that upper-shell rod bearing oiling is accomplished just prior to the point of highest loading. When you consider the system as a whole, it is not surprising that so many Chevrolet racecars manage to finish the race and run strong even with a stock oiling system. As long as you keep the pickup covered with oil, lubrication problems will be few and far between.
The best place to start examining the small-block oiling system is at the oil pump. The factory now offers only one oil pump for production small-blocks: the Z28 pump PN 3848907. This bulletproof pump has 1.20-inch tall gears and is standard equipment on all small-block engines. Chevrolet also offers a highvolume, high-pressure pump with 1.50-inch tall gears (PN 14044872). These pumps are supplied without a pickup unit because of the wide variations in oil pan design. It is always advisable to braze or TIG weld the pickup tube in place, but this should only be done after the relief valve and spring have been removed from the pump cover. Many backyard mechanics have ruined the relief mechanism by overheating while welding. Then they are puzzled when the engine loses oil pressure.
If you feel that your system needs more pressure, you can install the stiffer Chevrolet relief spring PN 3848911. Make sure the spring you get has a white stripe painted on it. Some engine builders like to modify the pumps by drilling lubricating holes through the idler gear and milling antichatter grooves in the pump cover and the pump housing. This equalizes the pressure on the gears and prevents oil cavitation at high engine speeds. Big-block oil pumps were originally used in smallblocks for just this purpose. Bigblock pumps also have additional gear teeth allowing them to operate more smoothly. However, the smallblock pump is still up to the task when properly modified, and it has a lot less drag than the big-block highvolume pump.
To finish preparing the pump, you should gently deburr all edges with emery cloth and then wash the pieces in clean solvent and blow them dry (also see the sidebar Oil Pump Tech Tips for more pump preparation tips). A basic step in assembling oil pumps is to treat them to a liberal coating of assembly lube on the gears, gear shafts, and the inner housing. The pump cover bolts should be sparkling clean and treated with Loctite to ensure that they stay secure.
Before you clean engine components for final assembly, take some time to gently relieve and radius the cavity in the top of the rear main cap. If you look down through the oil passage, you’ll see that it makes a slight jog about two-thirds of the way down. A long shank carbide cutter can be used to radius the hump and provide a straight, free-flowing path for the oil to follow.
To install a small-block oil pump correctly you should preassemble the pump and pump driveshaft before you insert it into the block. The intermediate driveshaft snaps onto the oil pump with a plastic retaining sleeve PN 3764554. See the sidebar Oil Pump Driveshaft Tech for tips on ensuring that your driveshaft has the proper end clearance. There is usually plenty of room, but in some cases where the intake manifold has been milled or the incorrect pump shaft is used, the shaft, pump, and distributor gear can stack solid. You should also be aware that the 400-ci engine requires an intermediate shaft with a machined relief to clear the larger main bearing bores. For cheap insurance, aftermarket sources can supply steel intermediate shafts with bulletproof steel retaining sleeves.
Oil Pans and Screens
A good pan to use on early blocks is the high-performance Z28 piece PN 465220 along with the semicircular tray baffle PN 3927136. This pan must have the thick, late-style rubber end seals; it will leak oil if you use the thinner, early seals. Strict budgets may require the use of a stock oil pan. Keep in mind that some factory pans have internal baffling, and these should be used whenever possible. Look for the type having a flat baffle welded into the front of the pan. This baffle is somewhat helpful in controlling oil slosh. Engines built before 1980 have a left-hand (driver-side) dipstick location, while 1980 to 1985 blocks have dipsticks on the right-hand side and some have pan-mounted dipsticks. Cast-iron Bow Tie blocks have pads for both right- and left-hand dipsticks, but they are undrilled.
If you are building an engine with the 1986 and later one-piece rearmain seal, you must use the single-piece oil pan gasket and the appropriate oil pan. Two choices are the Corvette 6- quart pan PN 10055765 or the 5-quart Camaro pan PN 10110837. If you require more capacity you can get custom late-style pans from CV Products in North Carolina. Early blocks that have been outfitted with the adapter to use the late one-piece rear sealmust use the 1986 and later gasket set, except for aluminum Bow Tie blocks PN 24502501 and race-prepared Bow Tie blocks PN 24502503 that are designed for pre-1986 oil pans.
There are several schools of thought when it comes to using custom or specialty oil pans and baffling. Most performance pans feature additional capacity. They hold additional oil that can make the difference between life and death for bearings at very high RPM, and they move the oil level away from the zone of turbulence beneath the crankshaft assembly. Engine oil tends to wrap itself around a high-speed crank assembly and act very much like taffy in a taffypulling machine. If the oil level is too close, whirling ropes of oil can be drawn from the sump and cause additional drag. Simply moving the oil level away from the spinning crank is enough to encourage additional oil to drop out of the rotating assembly. This is the idea behind the ultradeep pans used in many drag race engines. Deep pans and dry-sump systems serve a common purpose: to move the oil to a location where it will not be affected by the spinning crank. But in reality they only address part of the problem; they do nothing to actually remove oil from the crank assembly.
When windage trays were first developed, the idea was to prevent oil aeration, but they only served to bounce more oil back into the problem area. Once this deficiency was recognized, they were replaced by screens that allowed some oil to filter through, while a crankshaft scraper removed oil from the crank. Power gains proved that this was the right idea, and further investigation produced wet-sump systems that equal, and in some cases, out-power a dry-sump system. In racing applications this becomes an important consideration since the wetsump system is nearly always lighter than the dry-sump unit.
If you’re building a specialized street machine, you may find it helpful to equip the engine with specialty oiling components. In many cases they will offer the versatility you are looking for. Cars in this category often make use of deep sump pans from Moroso and Milodon, but you should always verify ground clearance before ordering a new pan. If you are forced to use a low-profile pan, these same manufacturers offer special designs that are approximately the same depth as stock pans but have widened sump sections to accommodate a larger oil volume. If you plan on using a windage tray, it’s advisable to purchase one compatible with the pan design to ensure easy installation. Try to avoid chrome oil pans in anything but a full-custom show car. The chrome tends to hold in the heat and partially defeats the purpose of your system. One final addition is the magnetic GM drain plug PN 23011420 that collects small metal particles and keeps them out of the bearings.
There are several oiling system components that are often overlooked. Chief among them is the oil filtering system. The small-block is blessed with an excellent design in this area, but it’s important to understand how the filtering process works so you don’t inadvertently perform a modification that degrades lubricant quality.
The original 265-ci V-8 introduced in 1955 did not have a provision for an oil filter, but all engines produced since then have full-flow filtered oiling. Until 1968, small-blocks used a canister-style oil filter that contained a replaceable cartridge. This is an excellent filtering system and there is no reason to change it. All 1968 and later engines came with the more convenient screw-on filters. Early blocks can be updated with an adapter kit, but keep in mind that both filters are equally efficient, and the filter cartridges cost less. Some engine builders even prefer canister filters, and they take great pains to convert later blocks to the early configuration. This can be made easier with the use of Chevrolet’s conversion kit PN 5574538.
Cooling, Plumbing, and Gauges Any good performance oiling system should be equipped with a radiator- type oil cooler. There are about a zillion of them on the market these days and some of them are very effective. Look for the types where the oil flows from one end to the other. This often produces the least restriction. Another important consideration is mounting hardware. Some coolers have very flimsy mounting bosses and they may break loose on rough roads. The best choice is a cooler with large 1⁄2-inch passages and a stout, fit- ted brace around the circumference. This allows sturdy mounting and good cooling without restriction. Names like Earl’s, Russell Performance, and Hayden will keep you on the right path.
A variety of specialty adapters are often needed when adding remote filters and coolers. Some adapters just screw-on like standard filters, and these require care to prevent leaks. Many of these quickie units also have restrictive passages that can cause a drop in oil pressure. Since there are so many on the market, make sure you check their design carefully before you lay out your cash. However, you won’t be far off the mark if you stick with proven pieces like those from Moroso, Trans-Dapt, and Traco. The Traco adapter is universally accepted, because it doesn’t leak and the passages are large and free flowing. It is drilled for 1⁄2-inch pipe fittings.
Fittingswithsharp90-degree turns and restrictive adapters/couplers should be avoided.Manufacturers like Earl’s, Russell, and others have special, high-flow fittings in all popular sizes and shapes. These fittings feature gentlebends, superior sealing, andtheyare compatible with standard hoses or braidedsteel lines. Ifyou’regoingtothe trouble of installing a remote oil filter and/or cooler, use quality hardware andyouwillavoidoilleaksanddelivery problems.
Another important aspect of the oiling system is the provision for monitoring oil pressure and temperature. Always take oil pressure readings from the pressure takeoffs at either end of the block and determine oil temperature by direct measurement in the oil pan, if possible.
Consider using an oil pressure gauge with a warning light, like those from AutoMeter. For years you’ve been told that gauges are the only way to go and that idiot lights are for idiots. Well, some of those “idiots” include big-name race drivers who are too busy racing to check all the gauges as closely as they should. A big winking red eye gets their attention every time, and that’s what really matters. So unless you’re a reliable gauge watcher, it’s a good idea to back up the system with a light or pressure switch that cuts off the engine if pressured drops dangerously low. And, whatever you do, don’t install an oil pressure gauge and leave the gauge light unwired. After all, you do drive the car at night, don’t you?
Dry-Sump Oiling Systems
Dry-sump oiling systems are recommended for all severe-service applications where not prohibited by rules. The efficiency and reliability of dry-sump oiling systems has made them the leading choice for oiling systems in nearly all racing applications.
Wet-sump systems simply store the engine’s lubricating oil in the oil pan with the pump and/or pickup submerged in the oil, while the more efficient dry-sump systems hold the oil in an external tank. In a wet-sump arrangement, the oil is poorly controlled. The forces of acceleration, braking, and cornering may cause the oil pickup to become uncovered, causing an interruption in the supply of lubrication. The oil may also cause a drag on the rapidly spinning crankshaft if a proper windage tray is not incorporated. This reduces horsepower and aerates the oil, which diminishes its lubricating capacity.
Dry-sump systems correct these problems and offer numerous advantages for high-performance applications. All of the oil is stored in a separate tank, thus removing it from the primary source of heat. An externally mounted dry-sump pump continuously scavenges the oil pan dry and routes all the oil to the external tank from which it is cooled, filtered, and returned to the engine under pressure. External tanks often hold 10 quarts of oil or more, thus ensuring a steady supply of engine oil under all operating conditions. Because no oil remains in the oil pan, the engine is unaffected by crankcase windage, and the oil pan can be made very shallow, which permits the engine to be mounted lower in the chassis to improve vehicle dynamics. Dry-sump systems also lessen the requirement for track cleanup after an engine failure, because there is no oil in the pan to foul the track surface.
Written by John Baechtel and Posted with Permission of CarTechBooks