Title: Racing Oil Systems for Mopar Engines
Date: June 2004
Author: Phil Haskins

Recently, I learned a great deal about Oiling Systems, Oil Pressure and Leaking Seals and every little aspect of building a fresh motor plays a significant role in achieving an optimum lube system without experiencing nasty leaks. Seal installation, fasteners, and last but not least, preparation of components all play major roles in sealing up our Mighty Mopar Motors. The following may be of help to those who are preparing to rebuild their power plants in the near future and those trying to find the magic number in respect to Oil Pressure for their particular application.

Race Oiling Systems for Chrysler Engines

Stock Lubrication Systems are adequate for normal driving and occasional high revs, but an all-out Drag Racing application will require some modifications to insure proper lubrication to the rod and main bearings in all Chrysler Engines. Race motors that exceed 5500 RPM on the strip need additional help to protect from premature wear. The following are some general considerations that apply to all Chrysler Corporation Engines.

Bearings

For increased Oil Flow to the Rod Bearings on all Mopar Motors, install upper main bearing shells with the oil groove in both the block and main bearing caps. This is particularly important for the 383-400 and 360 Engines. The Hemi Main bearings are fully grooved and these can be used in the 413-426W-440 Engines. Fully grooved race bearings are also available for the 273-318-340 Engines. For all out drag racing use, babbit bearings are recommended. For constant high load, high RPM use such as Nascar Series/Round Track Racing, hard bearings made of F-77 material are recommended. Maximum duty Federal Mogul Aluminum Bearings are advisable for medium duty off-road applications. All Chrysler Corporation Engines used for racing should have at least .0015 - .002” Crankshaft to bearing clearance. Crankshaft to bearing clearances over .0035 - .004 are undesirable because of increased engine oil demand.

Oil

For all-out Drag Racing applications, use at least a 30 weight high detergent motor oil. For Roller Cam Engines, a straight 40 weight racing oil is recommended, and for ultimate reduction in friction with high heat protection, use a Synthetic Motor Oil, something in a 5W-50 weight or 10W-40. Make sure you repair all minor oil leaks before using a synthetic motor oil, for some reason, synthetic oils seem to find all the leaking spots much faster than petroleum based oils. If using Synthetic Oils, you’ll find your engine idling a few hundred RPM’s higher and the overall operating temperature will drop about 5 to 15 degrees.

Oil Pumps

The stock oil pump is adequate for normal operation if it is up to specifications. The clearance between the outer rotor and the pump body should be less than .014”. The tip clearance between the inner and outer rotor should be less than .010”. The clearance between a straight edge laid across the face and the rotors should be less than .004”. The pump must turn freely when assembled. In cases where engine clearances are very tight, obviously you’ll experience higher oil pressures, but when clearances are as they should be, oil pressures should not exceed 85-90 lbs. at full engine RPM and 60-65 lbs at idle. If these conditions persists, you can expect seal leakage almost anywhere, specifically the rear main seals on B and RB engines. If clearances have been checked with Plastic Gage or through other precision means and are within normal ranges and you still experience very high oil pressures during idle and full motor RPM, you may consider changing the spring in the oil pump to a lighter-duty spring to relieve about 5-10 lbs. of pressure. Also check behind the threaded cap on B and RB engines, sometimes the factory placed a small shim behind the cap to increase pre-load on the factory springs, thus increasing oil pressure. Removing the shim will help reduce the pre-load on the spring and reduce the oil pressure somewhat. For all out high perfpormance racing engines, the Milodon Oiling System is far superior to the Mopar factory stuff.

Oil pump Drive

All Chrysler Corporation V-8’s us an oil pump drive shaft that also functions as a distributor drive. The gear on one end meshes with the camshaft and the other end is hex-shaped and fits into the oil pump. All the LA Engines, 273-318-340-360 use the same oil pump drive shaft and all B, RB and Hemi Engines use the same oil pump shaft. For racing purposes, there are two special considerations that make the stock oil pump drive inadequate. The racing high capacity, high pressure oil pumps turned at high engine speeds, load the tip of the shaft to the point that it shears off. Also, if Roller camshafts are used, the stock gear that meshes with it is incompatible with the camshaft and will wear out almost instantly filling the engine with metal chips. These two problems can be solved by using the specially designed racing oil pump drives. The shearing-off problem is solved by hardening the shaft’s tip. The gear problem is eliminated by replacing the stock gear with an aluminum bronze gear.

Oil Pressure Requirements

Generally, a good rule of thumb to use for oil pressure requirements is 50 PSI for 5,000 RPM of crankshaft speed. Then, add at least 10 PSI for each additional 1,000 RPM increment of crankshaft speed. I.E. 60 PSI for 6,000 RPM, 80 PSI for 8,000 PRM, and so on.