Mopar Action On-line – Tech Questions
Erin Bowhan, Eugene, OR, 1972 Dart Swinger 318
I am 16 and my dad and I are installing a 1975 318 in my ’72Dart, it has been bored .040″ and has high compression domed pistons. Italso has some kind of aftermarket performance cam in it that we have notbeen able to identify, we were told that it was an RV2 cam and my dad saidthat it should be good for torque. My dad is showing me how to gasket matchand “clean up” the intake and exhaust ports and we are installing anEdelbrock Torker II intake manifold with a Holley 80457 600cfm with vaccuumsecondaries and Hedman headers with dual 2.5″ exhaust that were all donatedby a sleeper 1975 four door Dart.
My question for you concerns the oil pump drive shaft/distributor drivegear. When we bought new main and rod bearings at the local parts store themanager who my dad has known for years, mentioned that he had a Duster thathad the oil pump drive break and wipe out his whole engine! He mentionedthat all of the stock ones were weak and that while we have the engine tornapart we should replace it with an aftermarket piece. Are all of theorigional shafts faulty or weak? My dad said he read somewhere that theproblem was caused by misalignment because of poor machining tolerances andthat not all oil pump drive shafts need replacing. We are on a budget and weare wondering if this is something we absolutely should replace while theengine is out of the vehicle and disassembled. Thanks for any help you canprovide, my dad said he trusts your opinion and if this is something youthink we should do he will go ahead and pay for it even if it is just forhis “peace of mind”. We are waiting to finish assembling our engine until wehear back from you.
Both statements are true. The stock shaft isn’t great, the MP shaft is muchbetter and worth every penny. And, yes, some rear main bearing caps weremachined with the oil pump seating area “crooked”, this will break ANY pumpdriveshaft. This is easy to check with a straightedge – this surface shouldbe parallel to the pan rail. If crooked, the cap can easily be corrected atany decent machine shop.