Читать книгу Modern Engine Blueprinting Techniques - Mike Mavrigian - Страница 11
ОглавлениеYour engine must provide a strong and steady supply of oil to all critical components. In essence the engine must deliver the correct volume of oil under a certain pressure to reach all the critical components during operation. If this does not happen, the engine experiences oil starvation and this obviously degrades performance. The engine’s vital components are also damaged, and this could lead to outright engine failure. In this chapter, I cover specific considerations for retaining and optimizing a stock-type wet sump oiling system and also the benefits of upgrading to a dry sump oiling system.
A “wet sump” system supplies pressurized oil to the engine’s rotating and reciprocating assemblies. Engine oil is stored in the big reservoir section of the oil pan. A mechanically driven oil pump picks up the oil, which obtains the sump’s oil via a submerged oil pickup. Depending on engine design, an intermediate shaft connecting the distributor shaft to the oil pump may drive the wet sump oil pump, or the crankshaft snout may drive a crank-mounted gerotor-style oil pump.
High-performance engines often benefit from a large-capacity custom oil pan. This oversize pan is installed on a Dart Big-M block fitted with a 4.750-inch stroker crank.
GM LS engines, as one example, have a crank-driven pump. Pressurized oil is distributed from this main source throughout the engine through the oil passages in the block, crank journals, main bearings, rod bearings, and eventually to the valvetrain. This system delivers oil to all required areas. In addition, the oil must be pushed through all of these passages to eventually route to the upper end of the engine. The oil is then free to drain back to the sump, with delivery and drainback serving as an ongoing cycle during engine operation.
In a wet sump design, the pump’s “pickup” is immersed in oil at all times and has a filtering screen. Depending on pump, engine, and oil pan design, the pickup has a short or long pickup tube that connects the pump to the pickup. If the oil pump is located directly over or very close to the oil pan’s sump, the tube length is short. If the pump is located at one end of the block but the sump is located at the opposite end, a longer tube is needed to locate the pickup deep inside the sump.
In-pan or wet sump oil pumps include (or require separately) a pickup assembly designed to be submerged in the sump reservoir. The distributor drives the pump, which is driven at half of crankshaft speed. In some cases, such as the old flathead Ford, the pump is driven by gears that engage with the camshaft gear.
Front-mounted crankshaft-driven oil pumps are commonly used on engines with distributorless ignition, and are driven at crank speed.
When fitting the pickup to the pump, test fit to make sure that the pickup is located close to the floor of the pan sump. Clearance should be approximately 5/16 inch or so between the pickup and sump floor. If the oil pump design has a press-fit pickup tube, press the tube into the pump using a pickup tube installer tool. This has a crescent-shaped head that allows you to capture the tube’s swedged end. With the pump mounted to the block, use this tool and a clean hammer to install the tube to the pump. Measure the distance from the oil pan rail to the sump floor. Then adjust the clock position of the tube at the pump to place the bottom of the pickup close to the pan’s sump floor. It measures from the block’s pan rail to the bottom of the pickup. With the pickup adjusted, use a marker to place matchmarks on the pump and tube. Remove the pump from the block and tack weld or full weld the tube to the pump. This ensures that the pickup tube doesn’t move or loosen.
When interference-fitting a pickup tube to an in-pan pump, a special open-center tool is required for installation.
If the oil pump is crank driven, the pickup tube has a slip-in fit to the pump and is sealed with an O-ring. A mounting tab on the tube bolts to the pump body. If you’re using a stock-type oil pan, no adjustment is needed because the pickup tube assembly is bolted down in a fixed position. The tube has another mounting tab or bracket that likely bolts to one of the main caps. Regardless of whether the pump is distributor driven or crank driven, if you’re using an aftermarket oil pan with a deeper sump, you must use the specific pickup assembly recommended by the pan manufacturer.
Once the pickup has been interference-fit to the pump and adjusted for pickup depth (to suit the pan), the tube should be welded to the pump body.
Billet aluminum pumps, designed for racing applications, have an integrated pickup and screen that require no external pickup tube. Because the pump bottom must be immersed in the oil supply, pump body heights are offered for specific oil-pan sump depths. This style eliminates the possibility of pickup tube leaks or vibrational damage.
Depending on design, the timing set must be installed prior to pump installation. Pictured here is an LS2 short block. Note that the pump is mounted ahead of the timing gear.
Crank-driven oil pumps have a driven gear that have a series of broad teeth.
The pump’s driven gear slips over and engages the drive gear, which installs onto the crankshaft snout. This OEM-LS drive gear has an integrated timing chain gear.
Billet race pumps are easily disassembled for inspection and cleaning. As with traditional in-pan pumps, pressure adjustments can be made by changing pressure relief springs.
A crank-driven oil pump likely has a lone pickup tube that is necessitated by the location of a rear-pan sump. This type of pump has a pickup tube that bolts to the pump and is sealed with an O-ring, so no interference fitting or welding is needed.
If the pump is located far from the sump, the tube will be long and require at least one additional support bracket to support the weight and length of the pickup tube. It is usually fastened to a main cap bolt or stud. Here is a stock type pickup on a GM LS engine. The sheet-metal tray seen here serves as a windage tray, which protects the crankshaft from oil splashback from the pan. This reduces parasitic oil drag on the crank counterweights and rod big ends.
Another type of gerotor pump is the billet style. It bolts to the block and has a built-in pickup with no external pickup tube. This style of pump is available for certain applications in which a specific oil pan is to be used. A big advantage of this type of pump is that there’s no press-fit pickup tube that might loosen up during engine operation, so there’s no concern about sucking air into the oil system due to a loosened or broken tube.
If you’ve decided to use an aftermarket oil pan with a deeper sump, pay attention to the oil level dipstick. Don’t simply assume that a dipstick “made for that engine” has properly placed level indicators. With the engine upright and at the level to which it would be installed in the vehicle, add the specified amount of oil that your pan calls for. Allow a few minutes for the oil to drain into the sump. Insert the dipstick and compare the fluid level to the marks on the stick. You may place different marks on the stick, or you may find that you need a longer stick. Aftermarket dipsticks are available that can easily be customized for fit. Flexible (woven stainless steel cable) sticks have a swedged-on tip that can then be cut to length at the top end. The upper end is secured in a billet-aluminum handle with a set screw.
Billet oil pumps have a built-in pickup screen.
The big advantage of the billet pumps is the elimination of a separate pickup, so pickup tube damage such as loosening or cracking due to engine vibration is eliminated.
A screened windage tray reduces oil splashback while permitting faster oil drain to the sump. A built-in baffle/windage tray is also featured on this pan. Note the square passage hole for pickup entry. Vertical baffle wall(s) in the pan prevent sump/pickup starvation during severe acceleration, braking, and/or severe lateral turns, depending on design.
A “dry sump” system uses a more direct manner to supply oil to the engine. A belt drives an externally mounted oil pump that uses external plumbing to flow oil to the engine. For a dry system, the sump is not placed in the oil pan; rather, it uses a remote reservoir. It’s typically mounted in a variety of locations under the hood of a street vehicle or in the cockpit of a race car. In very basic terms, the external pump draws oil from the remote reservoir and forces the oil through the plumbing. In this manner, oil can be directly sent to the main bearings through a block port and delivered directly to the valvetrain with one or two plumbed hoses, then directly delivered to a turbocharger, for example.
Dry sump pumps are offered in several configurations, depending on how many direct-delivery and return routes are required. This provides direct oil delivery to specific areas, and elimination of oil starvation caused by angle and centrifugal forces placed on the car. Thus, the oil pump never sucks in air, and the potential for oil aeration is eliminated. The scavenge section(s) of the dry sump pump draws oil from the dry sump pan. Vacuum is created and that draws excess oil from the surfaces of the crank and rods, and this mitigates parasitic drag. As a result, the engine operates more efficiently.
When plumbing a dry sump system, size requirements may vary, but a general rule is to use –10, –12 and –16 hose, fitting, and hose end sizes. For some turbo applications, a –6 hose size may be recommended to feed the turbo. Generally, a larger size is required for the return hose that runs from the pump to the remote oil reservoir. For instance, if –12 hoses are used for all feeds, a –16 hose is used for oil return to the reservoir.
Dry sump oil systems use an externally mounted oil pump, a special pan design, and a remote oil reservoir from which the pump draws oil. External plumbing allows direct oil delivery to specific areas of the engine. Oil returning to the shallow pan is then pulled, or scavenged, back to the pump, which returns the oil to the remote reservoir. Dry sump systems allow you to deliver oil directly to specific areas of the engine instead of relying on one central pumping source to send oil throughout the engine. Since a dry sump system stores the oil in a remote reservoir, the pan is used simply as a seal to the bottom end, resulting in a shallower pan for improved ground clearance.
Typical belt-drive dry sump setup (three-stage shown here). Oil is drawn from the remote reservoir to the pump, which feeds oil to the engine. Scavenge plumbing pulls drained oil from the pan and sends it back to the remote reservoir. (Illustration Courtesy Aviaid Competition Oil Systems)
Another example of a three-stage system, but here the pump is driven by the camshaft instead of using a belt drive. (Illustration Courtesy Aviaid Competition Oil Systems)
Threaded bungs are installed on a dry sump oil pan for suction line fittings in which the pump draws drainback oil. Tapping and fitting special adapters may be required for plumbing to the block or other areas. The aftermarket typically offers a variety of adapters for all popular blocks to supply oil to the block’s main galley at the stock oil filter location. By the way, if you’re using the OEM filter location for oil feed, you remotely locate an oil filter.
A pulley on the crankshaft snout directly drives a notched belt that connects to an externally mounted dry sump oil pump with most setups. Dry sump pumps, via the proper pulley diameters, are generally driven at about half the crankshaft speed. Dry sump pumps are also available that are driven by the nose of the camshaft, with the pump mounted on the face of a special timing cover. A dry sump system has many advantages: It has consistent oil pressure; the oil pickup does not become uncovered and starve the engine for oil in severe turns, acceleration or braking; oil pressure is adjustable; capacity is increased; the short-depth pan allows lower mounting of the engine in the chassis; and positive oil delivery to vital engine components. The engine also enjoys a cooler oil supply because the oil is quickly returned to the remote reservoir instead of being stored in the hot oil pan.
Dry Sump Stage and Section Designs
| Type | Pressure Sections | Scavenge Sections |
| 2-stage | 1 | 1 |
| 3-stage | 1 | 2 |
| 4-stage | 1 | 3 |
| 5-stage | 2 | 3 |
| 6-stage | 2 | 4 |
Dry Sump Oil System Components
• Dry sump pump
• Dry sump pump pulley
• Toothed pump drive belt
• Pump fittings (male –AN 37-degree flare to accept female –AN hose ends)
• Pump mounting bracket
• In-line screened oil filter(s)
• Remote in-line oil filter and filter mount
• Remote-mounted oil tank
• Breather (separate or on-tank)
• Oil filter block-off plate for engine block
• –AN hose assemblies as required
Sections and Stages
A dry sump pump has two sections. The pressure section delivers oil to the engine. The scavenge section pulls “leftover” oil from the dry sump pan and sends it back to the remote oil reservoir.
Dry sump pumps are built in stages, with one pressure section and one or more scavenge sections. The additional scavenge sections (as few as one, as many as six) allow oil to be scavenged more quickly and efficiently from specific areas of the engine, instead of waiting for the oil to be drawn into the pan for scavenge pickup.
Whenever dealing with aluminum (–AN) fittings and hose ends, always use a dedicated aluminum wrench to avoid damaging the hose ends and fittings.
Dry sump pumps have a series of individual pumps stacked together. These individual pumps are referred to as stages. Pumps are available in two-, three-, four-stage, etc., depending on how many individual oil feed and scavenge lines are required for a particular engine.
In order to relocate the oil filter to a remote location, a base adapter is installed to the block at the original filter boss. Using either –AN fittings or nipple fittings at this base, you can then run hoses to the remote filter adapter. Bases are usually marked for inlet and outlet locations. At the engine block base adapter, “IN” is for oil flowing from the filter to the block, while “OUT” is for oil flowing from the block to the filter.
Remote engine oil coolers provide heat dissipation for engine oil. Similar in function to a cooling-system’s radiator, an oil cooler serves as a heat exchanger, dropping oil temperature before oil returns to the block. In the event of an engine failure, where debris has flowed through the oil system, hoses and coolers may be very difficult to clean and difficult to verify as clean. If you scatter an engine, roach a few bearings, etc. do not place the existing cooler back into service. You’re better off replacing the hoses and cooler to eliminate the possibility of circulating trapped metal particles back into the fresh engine.
Oil Pump Service
Any metal or foreign debris that enters the oiling system and travels through the engine leads to failure. You need to service a dry sump system during the rebuild process. This includes disassembling, cleaning, and inspecting the oil pump for damage.
You can plumb in-line filters in the oil return lines during system installation and the filters provide important protection. However, don’t rely on the filter alone. Always inspect the pump.
A thorough cleaning of the system is necessary and many people often overlook this.
Flush all the hoses, especially if you’re using hoses that you can’t also visually inspect, such as a long hose or a hose fitted with angled hose ends. Often, the best approach is to simply replace the hoses because debris can stick to hoses’ inner walls. If you’re certain that the hose is clean, by all means feel free to reuse it. If you have any doubts, though, spend the money to replace it.
When servicing –AN plumbing, disconnecting an oil hose can result in a mess. Quick-connect fittings, originally designed for aircraft and racecar applications, are available. This is a coupler from Jiffy-Tite. The coupler is similar to that found on a compressed-air hose. Pull the collar back to release, and pull the collar back when connecting. The nice thing about these fittings is that they self-seal when disconnected, which eliminates an oily mess during servicing. They also allow quick and easy plumbing removal or installation without wrenches.
As you well know, engine oil lubricates the engine. But oil also absorbs heat from critical engine components and carries it away. The more available oil in the system, the more heat that can be absorbed. External oil coolers function as heat exchangers. The extra amount of oil in the cooler and cooler hoses adds more volume to the system. As oil circulates from the engine through the cooler and back to the engine more heat is released. This sends cooler and more viscous oil back into the engine. External oil coolers are generally plumbed with –10 AN hoses, which is equivalent to a 5/8-inch-inside-diameter hose.
The cooler must be clean. If metal debris has entered the cooler, you can’t risk using it again because you can’t be certain it’s completely clean. It’s not worth risking engine failure to use a contaminated cooler. Simply buy a new cooler.
Adequate oil always needs to be delivered to the rod and main bearings. In some engines, restricting the oil delivered to non-critical areas improves oil delivery to vital components. For instance, in old Pontiac 455 engines, the factory oil holes in the lifter bores are larger than necessary so they steal some oil going to the main bearings.
When these lifters bores are bushed in order to resize the bores, a smaller oil hole is drilled into the lifter bore liners. This intersects with the original oil holes but reduces the passage to around .040 inch. This provides enough oil for the lifters, while sending more oil through the main gallery to the main bearings.
Certain aftermarket blocks have “priority main oiling” where oil feed passages are dedicated to the main bearings without bleed-off to other areas, so the mains get all of the oil they need. In some blocks, the lifter oil passages running from the rear are plugged by the factory. That means when these passages are initially drilled, they’re drilled all the way through and then plugged at the ends.
Oil delivery to the distributor gear can be improved. You drill a small hole (about .020 inch or so) in the plug in-line with the distributor to provide a small amount of “dribble” lube.
A distributor-driven, wet-sump oil pump requires an intermediate shaft. Be sure to install the shaft through the bottom of the block (in the oil pump shaft bore) before installing the pump. A built-in stopper, which can be a diameter change on the shaft, stopper bumps on the shaft, or a metal clip on the shaft, prevents the shaft from exiting through the top of the block. Make sure you lubricate the intermediate shaft before installation.
Depending on application, oil may need to be restricted to reduce oil delivered to the top end to send more to the bottom end. Or an area that is normally blocked off may need a small bit of lubrication. Here a 3/8-inch NPT plug installed at the rear of the lifter galley in a Pontiac big-block is drilled with a .020-inch orifice to feed a bit of extra oil to the distributor gear.
Each block design has different possibilities and requirements.
The faster the oil returns to the sump, the better. Common methods of promoting oil drainback include smoothing all of the surfaces across which the oil travels. This includes slightly chamfering oil drain holes in the lifter valley and heads or taking advantage of coatings. Painting the lifter valley with Glyptol (a high-heat electrical armature paint) seals off the rough cast surface and provides a smooth oil return surface. If the surface isn’t prepped properly, however, the Glyptol can flake off.
With the intermediate shaft and pump in place during test fitting, verify that the intermediate shaft has a bit of vertical endplay. If it’s too long, this places stress on the distributor and pump.
If you’re dead-set on smoothing the rough cast surface in the lifter valley, simply spend a few hours with a bunch of abrasives on a die grinder. That way, the Glyptol doesn’t contaminate the engine over time.
Various specialty shops offer excellent oil-shedding coatings that provide a slippery surface to speed up oil travel. This type of coating can be applied to crankshaft counterweights, rods, the inside walls of the oil pan, and the inside wall of the timing cover. This application also helps to sling off oil from rotating parts to reduce parasitic drag.
With that said, for a street engine, don’t mess with any of these mods. It’s a waste of money, and chances are high that you’re not going to see any benefit. For a race engine, though, anything you can do to speed up oil return and reduce oil-cling drag from the outer surface of rotating parts is a good thing.
If your engine uses the distributor to drive the oil pump, an intermediate shaft provides the connection between the distributor shaft and the oil-pump input shaft. For performance use, opt for a high-quality aftermarket shaft made of hardened steel or chrome-moly steel.
The shaft has either a male hex profile or a slot at one end and a drive tang on the opposite end. The slotted end engages to the distributor and the male tang end engages to the pump. In most designs, the intermediate shaft must be installed from the bottom of the block. The shaft is likely be designed to keep itself captive in the block, so that it can’t be accidentally pulled out during a distributor removal. If the shaft has a hex body along the full length, it likely includes a stopper clip that prevents it from pulling up through the top of the block. Be sure to install the shaft before installing the pump.
During test fitting, with the block upside down, install the intermediate shaft and the oil pump. Carefully engage the pump-driven shaft to the intermediate shaft. Snug down the pump with its mounting bolts. You should be able to wiggle the shaft up and down in relation to the pump’s driven shaft. A bit of vertical endplay ensures that the shaft isn’t in a bind, placing undue pressure on the distributor and pump. Endplay clearance of around .060 to .080 inch is typically acceptable.
High-Pressure High-Volume Pumps
Bearing clearances create restriction to the flow of oil, which creates pressure. The oil pump produces oil flow and is regulated to promote pressure. Larger bearing clearances reduce pressure and flow. In turn, a pump with higher volume and higher pressure is required. Oil viscosity is also a factor. In very general terms, lower viscosity oil or lighter weight oil needs tighter bearing clearances. Larger clearances are better suited to higher viscosity oil.
About 10 psi for every 1,000 rpm is the desired goal. It’s better to have higher oil volume and acceptable pressure than low volume and high pressure. If your oil pressure starts to drop at high RPM, it’s an indication that a higher volume pump is needed. If you don’t have enough volume, you can’t generate enough pressure. Want more pressure? You need more volume. If you’re running loose bearing clearances, say, in the .0035- to .004-inch range, you definitely need a higher volume pump in order to create more pressure.
A higher volume pump moves more oil under pressure. Pressure drops occur as the oil leaks past the bearings. You want enough flow to keep up with the pressure loss. Any additional pressure (after overcoming oil leaks) causes the pressure relief valve to open and dump excess oil straight back into the block.
In a gear-type oil pump, oil pump gear length affects volume. The larger (longer) the gears, the more volume. Pressure regulator springs (which can easily be changed) allow you to adjust when the pump’s bypass valve opens (valve opens earlier, lower pressure; valve opens later, higher pressure). For example, Melling’s small-block Chevy M55 standard volume/standard pressure pump has 1.200-inch-long gears and is regulated at 55 to 60 psi. The M55A standard volume/high-pressure pump has 1.200-inch-long gears and is regulated at 75-80 psi. The M55HB high-volume pump, which has a 1.500-inch-long gearset, is rated at 70 psi.
If pump pressure is too high and the engine has tight bearing clearances, the pressure rises until it finds an escape path. A pressure relief valve in the pump releases pressure. Otherwise, pressure can rise to the point of bursting an oil filter. Certain engines can benefit from a high-volume pump, such as old Ford big-blocks that have cam-bearing priority oiling, which tend to starve the mains.
In a nutshell, if the engine is modified from OEM stock form, a high-volume pump should probably be your choice. In a stock engine that doesn’t need higher volume, you could do more harm than good, since you may be bypassing oil constantly, which increases oil temperature. In a dry sump system, it’s easy to obtain more pressure, since you don’t have a weak intermediate shaft to worry about (some dry sump systems run as much as 90 psi).
Engine pre-oiling requires sending oil throughout the entire flow circuit, including to main and rod bearings, cam bearings, cam, lifters, and rockers. If the engine has a distributor-driven oil pump, an oil primer adapter can be inserted into the distributor bore to engage and drive the oil pump using an electric drill. If the engine has a crank-driven oil pump, you need a pressurized oil source to deliver oil. A remote engine pre-oiler tank has an oil reservoir and an air bladder. Fill the tank with oil and use compressed air to pressurize the reservoir. Connect the hose to an oil port (or oil pressure port) on the block. When you open the tank’s valve, pressurized oil is forced through the engine’s entire oil circuit. It’s best to remove the valve covers to view the rockers. When you see oil exiting from the rockers, you know that a full prime has been achieved.
Pre-Lube Before Initial Startup
Always pre-oil any fresh engine prior to starting for the first time. Never fire a freshly built or freshly rebuilt engine dry! Oil must be delivered to all areas before starting any freshly built engine: main bearings, rod bearings, lifters, oil pump, rockers, etc.
Traditional Oil Pumps
If your engine has a traditional oil pump, the camshaft drives the distributor and the distributor drives the oil pump. First submerge the oil pump into a container of fresh engine oil, connect the intermediate shaft to the pump, and turn the shaft by hand. Oil should exit the outlet port of the pump. Finally, install the pump.
Before installing the distributor, use a pre-oiling adapter to engage the oil pump. With the valve covers off, turn the adapter driveshaft with an electric drill. Keep turning until you see oil at each rocker location. This may take a few minutes, so be patient. Install a temporary oil pressure gauge at the block’s oil pressure gauge port to verify that you’ve built sufficient pressure. At this point you can install the valve covers and distributor, and you’re ready to fire.
Gerotor Oil Pumps
If the engine has a gerotor-style, crankshaft-driven oil pump, you can’t drive the pump in order to pre-oil the engine. You need a remote oil pressure canister, which is a pressure tank with an internal bladder. Melling’s pressure canister prelube kit (MPL-101), for example, holds 4 quarts of engine oil.
First, add oil (depending on the model, this may take 4 quarts or more). Charge the tank with compressed air. Connect the outlet hose to a fitting that threads into a main oil galley port (located on the driver’s side of the block, toward the front, just behind the timing cover). LS blocks have a 16-mm x 1.5 threaded hole.
Connect the canister hose to the appropriate fitting (this should be supplied with the canister) and open the canister valve. Pressurized oil is then pushed throughout the engine’s oil passages.
Gear-Type Oil Pumps
In a gear-type oil pump, oil pump gear length affects volume. The larger (longer) the gears, the more volume. Pressure regulator springs (which can easily be changed) allow you to adjust when the pump’s bypass valve opens (valve opens earlier, lower pressure; valve opens later, higher pressure). For example, Melling’s small-block Chevy M55 standard volume/standard pressure pump has 1.200-inch-long gears and is regulated at 55 to 60 psi. The M55A standard volume/high-pressure pump has 1.200-inch-long gears and is regulated at 75-80 psi. The M55HB high-volume pump, which has a 1.500-inch-long gearset, is rated at 70 psi.
If pump pressure is too high and the engine has tight bearing clearances, the pressure rises until it finds an escape path. A pressure relief valve in the pump releases pressure. Otherwise, pressure can rise to the point of bursting an oil filter. Certain engines can benefit from a high-volume pump, such as old Ford big-blocks that have cam-bearing priority oiling, which tend to starve the mains.
