Engine Oiling
Words: Larry Shepard
The engine’s oiling system does not get much respect. What most people might consider the main part of the oiling system—the oil pump—is one of the last parts installed onto the engine assembly. The engine’s oiling system is supposed to keep everything that moves lubricated. The oiling system relates to almost every part in the engine but the vast majority of these parts are not thought of as actually part of the oiling system. So the oil pump gets all the attention given to the oil system. The biggest problem with an oiling system is that there is no margin for error. If the oiling system doesn’t do its job, you will have broken engine parts. Trying to figure out what happened first can be very difficult, but failure analysis is beyond the scope of this article. It is always a good rule in engine building and planning to upgrade the oiling system as you upgrade the other engine components.
Most of the popular V-8 engines use a somewhat similar oiling system, in theory more than specific part numbers, so to make things more compact and hopefully a little less confusing, I am going to use one engine—the 426 HEMI® Gen II—for my main example and then pick up some of the unique aspects of the other V-8 engines.
Starting with the largest single engine part, the cylinder block, like P5155072 for the 426 HEMI, siamesed-bore finished at 4.25", many oiling system aspects are already defined by the block itself. The oil pump, like the hi-capacity big block pump P4286590, bolts to the block (left front on the 426 HEMI) but most of the oiling passages are internal to the block and not easily seen unless you look closely. The blocks do many things in conjunction with the oil pump. First, it holds the oil pickup that provides the means for the oil to get from the pan to the pump. Once the oil gets through the pump it is now under pressure and passes out to the oil filter like P4452890 or HP version P4529805. There are many styles and logo appearances for the oil filter for special applications like resto engines. See the Mopar Performance catalog for photos of some of the styles. After the filter, the oil comes back into the block, and passes up to the main oil galley – on the right side (passenger side) of the block. The oil enters the main oil galley at the front and will progress toward the rear oiling each tappet along the way. It also oils the mains and the crank starting at the front—#1 main—and working toward the rear—#5 main is last. The oil comes into the main bearings from the block, so the bearings are important to both the oiling system, the block and the crank like P5007250, the .400" stroker for the 426 HEMI and big block wedge engines. There is an oil hole in the top of the upper bearing shell that allows oil into the main bearing. In some cases, there is also a groove in the lower shell that allows oil to flow around the bearing easier. Clearances in the bearing are very important. The crank’s job is to get the oil pressure from the mains out to the rods and rod journals. There are lots of oil passages drilled into the crank to allow this to happen. The rod clearances affect how much oil is splashed onto the cylinder walls, which help the rings seal and cut down wear. The piston pin, and piston and rings, are all oiled by the oil that comes from the rod and crank clearances.
At the rear of the crank is the rear main seal P4271961. This keeps the oil inside the engine but it must be installed correctly—it could be reversed and it would leak. On the front of the engine, this job is done by the seal in the front cover—chrome P4349813. The seal only is P4876280 and it is pressed into the cover. This front seal fits against the nose of the vibration damper.
The main oil galley directly feeds the cam tappets like big block hydraulics P4007767. The camshaft itself is oiled up from the main bearings—there is a vertical passage from each main bearing up to each cam bearing, like P5249711 big block. There is a hole in each cam bearing shell that allows the oil into the clearance. The oil now has to go up to the cylinder heads and valvetrain. This is done by a passage off the top of one of the middle cam bearings—typically #2 or #4—these passages are still in the block except for the Magnum® engine (see below). The oiling passage to the heads in the block has a matched passage in the cylinder heads. Older parts that were raced may have a restrictor at this location—deck surface, usually in the head but block deck parting line is also possible. If one is found, it is generally a good idea to remove the restriction. Additionally, many cams have an oil hole drilled through the #4 cam journal and in some cases the #4 journal is grooved. These small features help oil get to the cylinder head and valvetrain.
The cylinder head like P5153779 (426 HEMI aluminum) is next. The head gasket must have an oil pressure feed hole on the deck to match the block and head. One of the most unique aspects of the 426 HEMI engine relative to the oiling system is that the oil that gets to the head and valvetrain has to return to the crankcase by two oil drains in the front and rear, lower edge of the head. The wedge engines do not do this in this manner so the 426 HEMI head gasket must have the drain holes in the outer corners of the gasket. Once the oil gets to the head, it oils the valvetrain. The oil that drips off the end of the rocker arm and leaks out past the rocker shaft clearances and pushrod tips is used to lubricate the valves. This oiling is controlled by the valve stem seals – P5249661.
Once the valvetrain has been oiled, the oil has to return to the crankcase. This oil is caught by the oil pan like P4529884. The oil pan has capacity aspects—6-quart or 8-quart (deep sump) plus sump locations—center, front (vans) and rear (trucks) and front cross-member clearances. To get back to the oil pump, the oil has to get picked up by the oil pickup like P4529567 which threads into the side of the block. This is a 1/2" pipe thread which is the standard 426 HEMI size. The race blocks have this same size. The pickup must also match the pans depth and sump location.
At any kind of engine speed, all of this oil traveling around in the engine, you tend to have what is called windage losses. Spinning the crank, rods and pistons around through a fog of oil takes horsepower. To help control the oil and optimize power, use a windage tray like P5007345 for the 4.15" crank. The long stroke crank will hit the standard big block tray, and the windage gains are greater with the longer stroke. The oil that leaks out of the tappet clearance and flies up from the crankcase is very hot once the engine has been running and this oil sprays onto the bottom of the intake manifolds—use heat shield P4529431 to lower your manifold temperatures and keep the oil off the intake.
The oil pump is driven off the camshaft by the distributor drive, which is a shaft and a gear assembly. There are two for the standard pump setup: the flat tappet version P3571071 and the roller tappet one (either hydraulic or billet mechanical) P3690875 which has the aluminum-bronze gear.
Before I leave the HEMI engines, let’s look at the 5.7L and 6.1L HEMI Gen III to illustrate a point. With more engine speed and more power output, you would like to have more oil capacity. In the typical wet-sump oiling system used in production cars and trucks, this capacity is directly related to the oil pan or more correctly the size of the sump. The typical drag racing solution is to drop the sump – 8 quart pans, 2" drops etc. Without getting into expensive car rebuilds, there is a cross-member in front and steering linkage behind. For the new HEMI or the Gen III, Milodon has found a trick solution—an oil pan wider than the bottom of the block. This new Milodon HEMI pan has a very unique sump—added capacity for street use.
The 440 or big block wedge is very similar to the 426 HEMI in many oiling aspects. However the valve seals must be changed to P4120492 (3/8" stem) because the wedge heads use 3/8" valve stems where the 426 HEMI uses 5/16". You always want to use valve seals in street applications. The 440 big block may use a different oil pan like P5007807AB (6 quart, center sump). This pan uses 1/2" pipe pickup P5007848. All race blocks use the 1/2" pipe threads for the oil pickup but the stock 383/440 blocks used 3/8" pipe so they would have to be machined out to 1/2" pipe. The big block wedge uses dip stick P4349629 and it is always a good idea to re-calibrate the dipstick if the pan has been swapped.
The small block (318/340/360) or A-engine uses a different oil pump P4286589 that attaches directly to the #5 main bearing cap. The small block’s oil filter is on the right rear side of the block. In this location, it can cause difficulties with header/exhaust clearances so there is a right-angle oil filter adapter P5249624AB that allows you to tip it out of the way. The small block oil pans fall into two basic groups: the 318/340 pan like P5249062 and the 360 pan. The radius on the ends of the pans make them unique and not interchangeable. The 360 also uses larger main bearings. The A-engine also uses a different dipstick – P4349628.
The small block hydraulic tappet P3614321 is unique from the big block. The relationship between the oil galley and the tappet is different so they are not interchangeable. The Magnum engine—the 5.2L and 5.9L small blocks built from 1992 thru 2003—uses hydraulic roller tappets P4876054. The Magnum engines are quite unique because they are the only Chrysler V-8 that oils the valvetrain up through the pushrods P5249662 (set of 16). This means that the Magnum small blocks do not have the oiling hole drilled in the block and heads. The 1970 340 Trans-Am engines (also known as the 340 6-barrel) used mechanical adjustable rocker arms in the valvetrain rather than the stamped rockers used on all the hydraulic cams. These mechanical rockers required a special rocker shaft P3577086 which has banana grooves cut along the surface which helps spread the oil along the shaft to better lubricate the long sleeves of the mechanical rocker arms. If you get into bigger cams that require dual valve springs, and you need valve seals, use special small valve seals P3690963AB for the 3/8" stem valves in the A-Engine.
I have only scratched the surface, so if you have any questions, you may contact the Mopar Performance Tech Line (888) 528-HEMI (4364), refer to the latest Mopar Performance catalog or visit Mopar.com.
To view the entire article download the following pdf.
Larry “Shep” Shepard is a retired Mopar Performance engineer, author of numerous Mopar Performance books and a Michigan Motor Sports Hall of Fame inductee.
