Rear Main Seal

[67Camaro RS/SS 350]

I have my engine apart and I am replacing the rear main seal due to a leak, but I need to know which way it goes in. I am not sure if the guy before me installed it correctly as it's always been leaking. Here are some pics. As you can see, one side is solid and the other side has a groove around the circumfrence. Which side faces the harmonic damper? Thanks.

[Vegas69]

Picture one is correct from the rear of the engine.

[67Camaro RS/SS 350]

So the side with the groove faces the damper and the side with the hash marks faces the flywheel, correct?

[Vegas69]

Yep......

[67Camaro RS/SS 350]

Also, I was told to offset the seal and not put the engine half flush with block surface. That way the 2 halves don't come together right at the block surface?

[mroth]

I would look at the seal and observe that the seal is made when the inside oil is trying to pushout it makes the seal squeeze closer to the crank preventing leakage.

[67Camaro RS/SS 350]

If I leave some of the seal offset from being flush, will that cause problems? I should also put some RTV at each corner of the bearing cap like an oil pan gasket, right?

[67Camaro RS/SS 350]

After all the trouble I went through, pulling the motor, replacing the rear main and the head gaskets, I still have a leak from the rear main. What did I do wrong? I offset the seal and I put RTV on the corners before I installed the seal cap.

As far as the head gaskets, FelPro number 1094, when I began to fill the engine with coolant, I had a leak coming from the rear passenger side corner of the head. A leak like a siv. I thought the 1094 were the coated shim style gasket? Before I used the 7733SH-1 and I had only bubbling, but the 1094 had a leak like a river. Both the head and block were smoothe. I have since pulled the heads and replaced the gaskets with 7733PT-2. The compression has dropped from 10.388 to 9.780. I don't seem to feel much difference in performance, but I definately don't have the leak anymore.

[Vegas69]

Are you sure it's a rear main and not a intake or oil sender leak?

[406 Q-ship]

Or the oil pan? Did you use the one piece pan gasket, or the 4 piece set? The oil pan itself can be warped, twisted, or the pan can be cracked. Are the valve covers leaking down the back of the engine making it look like a rear main seal, this goes along with the rear of the intake as Vegas says. I have found that the majority of "rear main" seal leaks are something else. I hate leaks at the rear and bottom of an engine!!!

[67Camaro RS/SS 350]

I am quite sure it is the rear main. If you look up to the rear main, you can see it is wet. If it was the intake or a valve cover, the pan area at the rear main wouldn't be wet because those two can't get to the pan. Those 2 have to run down the bell housing. The oil is coming from between the bell housing and the flywheel. The leak is not that bad, but I can't stand leaks of any kind. I was told to not worry about it. I may have to do just that. I am thinking of selling the newly .040" over bored, line bored block, pistons, rods and crank I have waiting to be assembled in favor of a newer 1pc rear main style. I, for some reason, have never had any luck with the 2pc style.

[Vegas69]

It can get to the rear main seal throught the bellhousing mating surface.

[406 Q-ship]

You'd be suprised where oil can get from a leak. I will say that you still could have an oil pan leak at the rear main cap besides the rear main seal. You said that the block was line bored, that can cause issues with the rear main seals ability to seal up I have heard, I never had an issue with my 400 but it was not line bored. Isn't there a shim that gets put behind a rear main seal on a 400 block that have been lined bored, if my memeory is still dependable.

[67Camaro RS/SS 350]

You'd be suprised where oil can get from a leak. I will say that you still could have an oil pan leak at the rear main cap besides the rear main seal. You said that the block was line bored, that can cause issues with the rear main seals ability to seal up I have heard, I never had an issue with my 400 but it was not line bored. Isn't there a shim that gets put behind a rear main seal on a 400 block that have been lined bored, if my memeory is still dependable.

This is not the block that has been line bored and it is also not a 400 block. It is a 71 350. The block that was line bored is also a 350, but it is a 73 block.

I also did use a 1pc pan gasket. I tell you, I have had better luck with leaks when I used a 4pc gasket.

[Mark Antrim]

This is a stretch but you do have a pcv system on your car? Your not building crankcase pressure and that is where it is blowing out at? Probably not it, but just something to look at.