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1972 350. Any downside to just installing the offset rear main seal? (BS 11829-1) Also trying the one piece OS 34509-t gasket. Will use Permatex 25228 in the corners. I figure just go with the offset and know I have fresh surface. First time for the one piece pan gasket, looks like a great idea. Thoughts?
Good plan, but stuff happens; and may not present as expected.
If, IF pan has ever been changed for any reason, it may now have a slightly later version pan; which do use a different gasket (OS34510-T)
In addition to where the seal's lip rides, the rear journal may have other damage; unlikely, but always possible.
If pan's never been off, be sure to dig out of sump & strainer, any bits of nylon-cladding; thrown from OE Cam sprocket.
Suggest do Not use "the Right Stuff " here. It's good for other apps but not here. Instead use a common hi-temp RED or Grey Or Black RTV
Follow the gasket maker's instruction and don't try to re-engineer what the pros did.
Ensure pan's flange is flat + square and bolt-holes are Not deformed-dimpled around their openings (small ball pein hammer + block of wood + patience).
Cleanliness is paramount ! Absolutely No vestige of old gasket-sealer anywhere on block or pan !
Just prior to gasket positioning, wipe each & every gasket metal surface with lacquer thinner/acetone & flash off. The gasket design requires it to "gain a purchase" on metal surfaces: if you smear them with RTV, (Please Don't) that gasket will squirm as you tighten bolts and it'll leak sure as the sun rises.
FYI: the one-piece pan gaskets became OE on later Gen 1 sbc engines; those engines' GM FSMs detail how to properly install.
Last edited by Rebelyell; May 26, 2026 at 02:02 PM.
great points, This pan has been off before, I will measure the pan to be sure thick or thin gasket, what do you think about permatex aviation #3, pn 80019, I've always had good luck with this. Otherwise this is pretty straightforward.
great points, This pan has been off before, I will measure the pan to be sure thick or thin gasket, what do you think about permatex aviation #3, pn 80019, I've always had good luck with this. Otherwise this is pretty straightforward.
hold my beer... .. local mechanic did my rms twice and it still F_)(* leaks... obviously gotta find a new mechanic to take care of this as I hate oil leaks.. hope it goes well for you...
I told ya which of three RTV to use, which to not use
GM FSM for later roller blocks specifies RTV GM P/N 12346141, you can look up the cross the Permatex that number's probably been superseded No science by due diligence & attention to detail.
I told ya which of three RTV to use, which to not use
GM FSM for later roller blocks specifies RTV GM P/N 12346141, you can look up the cross the Permatex that number's probably been superseded No science by due diligence & attention to detail.
good luck w/ your project
Why do you suggest not to use The Right Stuff in the corners?
Last edited by sleepchamber; Yesterday at 06:47 AM.
I just did this and have zero leaks. I used the offset seal - compare it to the one you take out to see which was in use to begin with, you'll be able to see any wear patterns once you have it out. You can Google up how to do it, it's pretty easy. I used a very slight swipe of RTV on the ends and make sure to leave one end sticking out about 3/8" so they are offset from the corner you'll be sealing with RTV as shown in the video.
For the pan gasket I used Permatex Ultra Grey 82194. The Fel Pro video pretty much says it all.
When you have the pan out you should check the bolt holes and flatten them out.
I did this exact same job two years ago to date with zero leaks since. I used the same advice the these guys are giving you. A while you’re in there job that I couldn’t recommend more is to replace your OE plastic connector oil pump drive shaft with an all steel one. It’s like twenty bucks and in stock at o reilly. I huge peace of mind upgrade.
Why do you suggest not to use The Right Stuff in the corners?
That stuff final cures to consistency of concrete and can be a real bear to disassemble. The recommended grades in FSM seal as well or better and do not present such disassembly issues.
Moreover, If ya keep on hand every type RTV available, you'd have hundreds & hundreds of dollars tied up for naught. Everything in moderation. Trust The General for recs.
Just because something's the latest & greatest doesn't mean it's the best.
rear seal and oil pan
.. local mechanic did my rms twice and it still F_)(* leaks... obviously gotta find a new mechanic to take care of this as I hate oil leaks.. hope it goes well for you...
