I've got a 390 (supposedly) that's running like a swiss watch, but is throwing oil like all get out. I don't know if it's from the rear main or someplace else on the rear of the engine (just put a aluminum intake on about 8 months ago). Would the oil pressure go down if the rear main was going bad? This engine only has about 8 thousand miles on it.

Thanks,
Butch Whitehouse


'74 F-250 4X4 (The object of my affliction!)
'96 F-150 4X4
'99 D'Elegant E-150 Conversion

 

 

You may well not see a significant reduction in oil pressure if the rear main was leaking.

There's a good chance it is a result of your manifold swap. The FE is notorious for leaking between the block and the manifold at the rear. Take a good luck back there and see if there is oil on the back of the block. You should be able to tell right away if the leak is up there or somewhere down below. How did you seal the rear of the manifold to the block?

 

Could be one of the plugs on the rear of the block has started to leak if they weren't put in right. This would reduce oil pressure but they are a pain to get to. You have to separate the trans, remove the flywheel and motor plate to see them.