I'm working on a really bad oil leak from the rear of the engine. So far I've pulled the pan and put new gaskets on. I've pulled the rear Babbitt and checked that all out. I put all back together and ran engine for ten minutes or so. I then noticed oil coming from the back of the engine still seems to be the passenger side which is the cam side. I don't know if its a gasket or seal or plug that keeps the rear of the cam from leaking? I'm now in the process of pulling the engine to check for the leak. My friend and I decided to pull the head and see what that all looks like. It ran good with a good amount of pep. It did smoke a bit especially when revving the engine. With the head pulled as you can see from the pics I got a ton of carbon, or oil. Don't really know what do you think. The cylinder walls all feel perfectly smooth with no scoring or scratches that I can feel. When I hand rotate the engine I do get a good bit of oil on the walls. Is that normal or are the rings shot or going bad?
Pulled head and oily
- Thread starter captain j
- Start date
Mike V. Florida
Well-known member
I agree with Columbia's diagnosis of the leak. I rub some #2 Permatex on the gasket over the camshaft bore and immediately around it. I rub it into the gasket material so it does not change the thickness.
Before worrying too much about the crud on the block, how many miles on it? If there are many miles on it and it runs well I would clean it up and put it back together and run it for just touring and driving. If it has only a few miles, or you are into high performance, different question.
However, I do wonder how you get a "good bit" of oil on the cylinder walls by "hand rotation" (hand crank)? It takes a lot of force to splash oil onto the cylinder walls and I have never heard of anyone doing it by hand.
Before worrying too much about the crud on the block, how many miles on it? If there are many miles on it and it runs well I would clean it up and put it back together and run it for just touring and driving. If it has only a few miles, or you are into high performance, different question.
However, I do wonder how you get a "good bit" of oil on the cylinder walls by "hand rotation" (hand crank)? It takes a lot of force to splash oil onto the cylinder walls and I have never heard of anyone doing it by hand.
Tom Wesenberg
Well-known member
I've also seen a cracked valve cover. The only way I can see that happening is by very uneven tightening of the bolts. Just like a head or oil pan, snug them all finger tight, then a bit more, then the final tightening, which doesn't have to be real tight. Put a box wrench on them and just a comfortable hand snugging is good.
James Rogers
Well-known member
If you use original bolts, you don't have to do this. The originals will all come out with no problem when removing the valve cover.
I think the leak is coming more from the back of the engine. I cleaned up around the valve cover and didn't see oil around there. Yeah the engine is filthy! Odometer has around 28000 on it and it is the original engine. I don't mind the engine smoking and burning oil "if that is fairly normal on a model a". ??? Ill also replace the rings if it needs it. The cylinder walls seem fine, I just wasn't sure if getting oil on the walls after hand cranking the engine was normal.
James Rogers
Well-known member
I see lots of people here claim their cylinder walls are "fine" just because the walls are slick and shiney. Truth is, you cannot tell the what condition of the cylinder wall to rings is without removing the pistons and rings to measure end gap. You can measure the bores in a couple of places but this won't tell you if the engine has been "overhauled" and larger rings installed, can't do that but once and that is suspect. Do some measuring and have a competent mechanic look at the engine, then make your decision. You don't want to throw good money after bad.
Residual oil left on piston and ring tops will smear on the walls when rotating the engine and yours look like they have lots of oil to smear.
Be sure to check the rear main cap for cracked babbitt and worn thrusts. I think you will find either a broken thrust or an out of clearance thrust. To check the thrust with the pan off, use a screwdriver to pry the crank forward and use feeler gauges to measure the gap between the front thrust and the crank. Anything over .012 will leak and the more it is the worse the leak. You also mentioned you checked the babbitt, did you measure the clearance or just do a cursory visual inspection? If you didn't measure it correctly and the clearance is more than .002 it will leak and all your work is for naught. If you think the gasket between the housing and block is leaking you have to pull the engine to check that and there is no good check except to replace the gasket when you are in there.
Just my honest, experienced opinion.
Residual oil left on piston and ring tops will smear on the walls when rotating the engine and yours look like they have lots of oil to smear.
Be sure to check the rear main cap for cracked babbitt and worn thrusts. I think you will find either a broken thrust or an out of clearance thrust. To check the thrust with the pan off, use a screwdriver to pry the crank forward and use feeler gauges to measure the gap between the front thrust and the crank. Anything over .012 will leak and the more it is the worse the leak. You also mentioned you checked the babbitt, did you measure the clearance or just do a cursory visual inspection? If you didn't measure it correctly and the clearance is more than .002 it will leak and all your work is for naught. If you think the gasket between the housing and block is leaking you have to pull the engine to check that and there is no good check except to replace the gasket when you are in there.
Just my honest, experienced opinion.
James Rogers
Well-known member
Here are some pictures of a rear main out of an engine I did the mains last week. Not only were the wells cut extending into the pan area at the front and there was no oil groove but it has an almost imperceptible crack at the front. I believe not having a groove may not have caused the crack but did contribute to it. This crack along with the wells being cut too far into the front of the cap and the bearing out of specs, caused the engine leak at the rear. Check that cap close, all these factors must be correct.
Attachments
Good info James ill check that main when I pull the pan again. I don't know what a thrust is? Also what do you think would cause all the black on top of the valves and piston? Is it oil or carbon buildup? Seems oily to me so would that come from the to rings or could it come from somewhere else?
700rpm
Well-known member
I'm nowhere near James on this stuff, but I just encountered the same thing on #4. My mechanic looked at it and concluded that the valve guides were leaking (they were black on the inside) and the buildup of carbon on #4 was due to oil being fried by a leaky exhaust valve. His prescription was new guides and grinding the valves.
Last edited: