[78w72]

Hope you can confirm where its coming from, smoke test is a good idea but at this point if you have wiped it all dry around the leak then went for a drive & saw where its wet only on the rear of the pan & not up by the filter housing, filter itself or valve covers etc... i think youve found the source of the leak.

Im pretty sure the rubber U seal isnt supposed to have RTV on it, just the corners, unless the bop gasket is designed different, those early 3 hole pans/gaskets are known to heave problems sealing, the later 5 hole design is better but still not as good as the cork gasket around the main cap.

[HWYSTR455]

I never use OE pans, or the BOP 1 piece, so can't comment on the install method.

But it does look like the RTV is a little light on the cap/block/pan corner:

.

[HWYSTR455]

What's you breather setup, the OE one to the air cleaner assembly?

Maybe try an open type breather on one of the covers? That would eliminate any concerns over crankcase psi.


.

[grivera]

I have the 1-piece seal on both cars and don’t like how thin the rubber section over the main cap is on mine and it looks thin on the pics here as well.

[Vid]

Originally Posted by Verdoro 68

Yeah, It does look dry. I always lube the gasket, but maybe I haven't been lubing it enough. I usually dip my finger in oil and give the seal a pass.

I go one step further than oil and use some wheel bearing grease like red n’ tacky. About 40 years ago I experienced an oil filter gasket leak similar to yours on a 302 SBC. I apparently didn’t use quite enough of the “oil on fingertip” method and the gasket grabbed and crinkled just enough to generate a minor but annoying leak. Ever since then I carefully give the gasket a neatly applied but ample dose of quality grease and I always wipe down the mounting boss at least twice before installation. Ever since, my leaks are from something other than the oil filter gasket, haha.


Sent from my iPhone using Tapatalk

[Verdoro 68]

Originally Posted by HWYSTR455

What's you breather setup, the OE one to the air cleaner assembly?

Maybe try an open type breather on one of the covers? That would eliminate any concerns over crankcase psi.


.

I have the stock setup to the air cleaner right now. I have a breather on the way for the driver's side, we'll see how that does.

Originally Posted by 78w72

Hope you can confirm where its coming from, smoke test is a good idea but at this point if you have wiped it all dry around the leak then went for a drive & saw where its wet only on the rear of the pan & not up by the filter housing, filter itself or valve covers etc... i think youve found the source of the leak.

Im pretty sure the rubber U seal isnt supposed to have RTV on it, just the corners, unless the bop gasket is designed different, those early 3 hole pans/gaskets are known to heave problems sealing, the later 5 hole design is better but still not as good as the cork gasket around the main cap.

I'm fairly certain it's the pan gasket. The instructions say to use dabs of sealer on the corners, but you're right, they don't say to use it on the U seal. I was so paranoid about leaks, I figured I'd do a little extra around the back. Oh, the irony!

I do have to wonder - if it's leaking with RTV at high RPMs, wouldn't it be worse without it?

["QUICK-SILVER"]

If the slots in the pan are over the groove in the main cap how does the gasket get compressed so oil doesn't leak out the slots?

Gasket thick enough to work with a grooved rear main cap would be too thick for a non grooved cap.

And did you use any sealer at the parting line between the rear main cap and block?

Clay

[grivera]

Good point on gasket thickness- seems the design is best for a non-grooved cap

[Verdoro 68]

Smoke machine worked like a charm - and quickly! I put the tube down in the valley pan down the hole for the PCV and within a minute or two I had smoke pouring out of the rear main area.

Hard to say if it's the pan gasket or the rear main as the smoke was coming from the center of the U area of the pan in droves. I believe mgarblik said to expect some smoke from the rear main, but this was enough to be concerned about. Oddly, no smoke from the corner of the oil pan or the side that was showing the cascade.

Whether it's the pan gasket or the rear main, I'm going to have to pull the engine back out to fix this.

[Gach]

That sucks !

[Verdoro 68]

I had a heck of a time finding the rear main that would seal up on the stand (one and two piece leaked on the tip test, graphtite did not). I glued the heck out of the pan gasket around the back area, so I'm guessing it's the rear main after all.

When I get this thing out, I'm going to smoke test it before it goes back in!

[jhein]

That's horrible news. I'm totally bummed for you. Since you've had so much trouble with leaks, once you get it fixed, maybe try to get access to a run stand to check for leaks before you put it back in?

Oh, I already forgot about your smoke machine! No run stand needed.

[Verdoro 68]

It’s a bummer, but if this is the worst problem I have with this build, I’m ok with that. Pulling the engine will give me a chance to look at how things are wearing too.

It’s a weekend job to pull and reseal. Parts are cheap considering what I’ve put into this thing. I just want to make sure it’s going to seal!

[mgarblik]

Originally Posted by Verdoro 68

I had a heck of a time finding the rear main that would seal up on the stand (one and two piece leaked on the tip test, graphtite did not). I glued the heck out of the pan gasket around the back area, so I'm guessing it's the rear main after all.

When I get this thing out, I'm going to smoke test it before it goes back in!

Well, the good news is you found the area where it's leaking. Also, the low cost smoke machine worked well for you. You will use it for all kinds of other stuff too. Open a disco! We smoke test every engine before it leaves the school. Out of 14 engines this year, 4 of them had some kind of issue, so your not alone.

[jhein]

Originally Posted by Verdoro 68

It’s a bummer, but if this is the worst problem I have with this build, I’m ok with that. Pulling the engine will give me a chance to look at how things are wearing too.

It’s a weekend job to pull and reseal. Parts are cheap considering what I’ve put into this thing. I just want to make sure it’s going to seal!

You put the Energizer Bunny to shame. Really.

[78w72]

Good to see the smoke machine showed the leak... it could be the rear main seal itself but after my experience with the older 3 hole pans, i still lean towards it being that U seal on the pan/gasket.

even if its the main seal, theres a 50/50 chance its the main or pan gasket, might be a good idea to go with a standard felpro gasket & use the cork for the cap to pan, sure would hate to find out it wasnt the rear main & end up in the same boat as now with the 1 piece.

my pan gasket leak required the engine to come in/out 3 times, 1st time i installed it & found a smaller leak after ~50-100 miles. pulled it to have the shop redo the rear main & found it leaked worse at just a few minutes idle time, pulled again to have them fix it & found it wasnt the rear main it was the rubber U seal on the pan gasket all along. cork U seal fixed the leak & still dry today. after all that & past engine installs, i can just about pull/install this motor with my eyes closed now!

[dataway]

Here is what my all stock setup looked like after assembly ... yes, all stock. Obviously I didn't like the look of that. Ended up using a BOP one piece oil pan gasket and just squeezed the thick section into the that "U".

Passed the tilt test fine, and hasn't leaked a drop so far ... but I haven't run it hard.

[Verdoro 68]

I spent quite a while making sure this thing was sealed up as best I could before I dropped it in. I’m curious to see what went wrong.

Looking closely at the tiny bit of crankshaft that’s visible, I think I see a frayed bit of main seal. You can sort of see it in the first pic I posted above - right around the bottom of the slot in the oil pan. Might be nothing, might be something. I guess I’ll find out when I yank the engine again. My wife will be thrilled.

[78w72]

worth reading this for best practices sealing up the oil pan or the rest of the pieces on a pontiac engine...

https://pontiacstreetperformance.com/psp/Sealit.html

[Singleton]

I'm thinking that with the engine out and flywheel off, that you could better determine if it's leaking at the main or the pan using the smoke tester. Maybe with engine upside down, (oil drained of course). Was any type of anerobic sealant used between the main cap and the block surface before bolting down? Oil can migrate there also.