oil leak between oil pan and timing cover

[old Chevy guy]

I've been reworking the old truck for awhile now. The chassis has been painted, the cabs been replaced, so on and so on. So while the motor was out I washed it up and threw some paint on it and changed all the oil gaskets. The oil pan and timing cover were pretty rusty so I swapped them out for some different ones, both were aftermarket neither new but in good shape. After I got it all in and running it was leaking from between where the pan meets the timing chain cover, a lot, like there is a gap. Today I took the timing chain cover off and was able to pop it right out without loosening the pan at all. Thinking that somehow the pan or cover was off I tried to compare the gasket fit on the old pan between the old and new timing chain covers and both fit badly. the rubber gasket is just plain to thin. Is this the wrong pan gasket set somehow or what's going on? I feel like back in the day I remember getting more than one set of rubber end gaskets when you bought a pan gasket, some thicker ones and some thinner ones, but I could be wrong. Has anyone else ever run into this? Its a 71 350 nothing high tech about it. Didn't leak there before shouldn't have ''fixed it'' I guess.

[kenn]

Hello Yes I think there are two different depth pans at that area.
I cant help with the differences now (at work) but when I was rebuilding my 79 350 the directions were with the seals.
K.E.N.

[Wrenchbender Ret]

Somewhere in the late 60's they changed the oil pan & timing cover using a thicker seal between them. If your pan & cover match you need the thicker seal.

[GRX]

Grumpy Page:
http://garage.grumpysperformance.com...n-gaskets.206/

Fel-Pro image:

[Redline novdog]

Good info for all to use GRX.Thanks!

[Gromit]

The answers from the forum members above are very likely your right answers - but my crankshaft seal leak turned out to be something unexpected so I wanted to put this out there.

Actually you are asking about the front seal and my two cents actually relates to the rear seal.

In my case it appears that the previous owner tried to put RTV into the rear seal - possibly in the process of attempting a real seal replacement without pulling the engine (which doubtless lots of folks on this site are fully capable of doing without a hitch with one of those installer kits with the wire tool that feeds the new seal around the crank and its seat with the engine in place.)..

But in my Gen 1 350 chevy's case some of the RTV he goobered in there had attached itself so firmly to the crankshaft seal surface that after it cured and when the crankshaft spun up this glob of RTV didn't just get peeled off like we would expect - instead it remained firmly attached to the crank surface and actually eroded away the new rubber seal as it spun around and around..

If you look at photo 2306 it looks like another glob of RTV but actually that is the totally galled up rubber seal

Image 2311 I'm skeptical about as a possible second source of my crankshaft seal leak- but I noticed upon disassembly that the two halves of the seal were offset about 4 millimeters from the seal support - maybe that is by design so I only mention it in case I'm wrong to think that might be a concern.

I wouldn't have believed it about the RTV myself if I didn't see it.. that was most definitely where mine was leaking

Photos attached.

Like they say; when diagnosing and you hear hoofbeats, think horses, not zebras - mine turned out to be a zebra.

[hamjet]

<<<<Image 2311 I'm skeptical about as a possible second source of my crankshaft seal leak- but I noticed upon disassembly that the two halves of the seal were offset about 4 millimeters from the seal support>>>> Alot of good ideas to look for, as to the two halves offset, the felpro gasket set for my 348 said to offset the two halves on the rear seal, maybe thats why they're like that in your case..

[old Chevy guy]

The problem was the need for the thicker front pan seal. The old pan measured like that too so not sure if the old pan was already a replacement of if my engine is really newer than I thought. Always thought it was the original . It has a two barrel on it which I figured out recently was not correct for a 71 with a 350 but figured somebody swapped the intake, now who knows? I will have to get the numbers and decode it and see what's up with that. When I changed the rear main the directions said to offset the ends also. The research I did on the oil pan issue said that the break year for that change was 1975 and up had the fat one but that was the only difference in the pan gasket. I also threw in a new chain and gears which I failed to do before. Upon closer inspection its a good thing as the original nylon was all cracked.