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Old 01-27-2008, 07:51 PM
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Installing Rear Main Seal - BBC

putting my motor together. Checked bearing clearances, oiled the bearings, etc. Ready to put on the last main bearing cap and rear main seal and start torquing everything down.

Question: Should I use some RTV around the rear main seal and rear main cap area? Just a very thin film perhaps. Or am I safer and better off using nothing except the rear seal itself? I have a Gen IV block, 454 and it has a 2-piece rear seal. I have 2-bolt main caps.

For some reason I don't trust the rear seal, even though it's new, to completely seal 100% back there. I hate oil leaks.

lee

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Old 01-27-2008, 09:19 PM
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i put a very small amount of red rtv between the two halves and torqued it down that way. i didnt put anything between the seal and the caps, though. this worked for me on the last two bbc rebuilds i did. i know, i hate a leaky car, also. i may have the ugliest, no body work or paint job, scratched, dinged car at the cruise spot......but i dont leave a puddle either! LOL.
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Old 01-28-2008, 06:26 AM
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Quote:
Originally Posted by timemachine
i put a very small amount of red rtv between the two halves and torqued it down that way. i didnt put anything between the seal and the caps, though. this worked for me on the last two bbc rebuilds i did. i know, i hate a leaky car, also. i may have the ugliest, no body work or paint job, scratched, dinged car at the cruise spot......but i dont leave a puddle either! LOL.
ok, thanks.

I'll wait for other replies also. If I thought it wouldnt effect the bearing clearances I'd pile the RTV all over the place back there. but I am concerned that if I put RTV between the two bearing halves that it may increase the bearing clearances a few thousandths? I don't know.

I'm considering doing it though. Just a very thin film of RTV between the two bearing halves and maybe a little more around the seal itself where it meets the bearing cap and block

anybody got any suggestions?

Lee
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Old 01-28-2008, 06:44 AM
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Don't but anything under the bearings themselves, it is paramount that the block and cap are perfectly clean before you install the bearings!!

I always clock my rear main seals so that the parting line is offset from the cap and block and a little bit of sealer on the seams is all I use. If your crank has a wear mark from the old seals, they do sell offset seals also.
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Old 01-28-2008, 06:49 AM
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Quote:
Originally Posted by 6426yy
Don't but anything under the bearings themselves, it is paramount that the block and cap are perfectly clean before you install the bearings!!

I always clock my rear main seals so that the parting line is offset from the cap and block and a little bit of sealer on the seams is all I use. If your crank has a wear mark from the old seals, they do sell offset seals also.
yes, I've seen that little trick about offsetting the 2 seal halves so they don't line up with the parting lines. I'll do that.

What about a tiny dab or RTV where the 2 seal halves meet? Where the ends touch eachother?

Lee
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Old 01-28-2008, 07:07 AM
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Quote:
What about a tiny dab or RTV where the 2 seal halves meet? Where the ends touch eachother

That's what I do.
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Old 02-27-2008, 09:20 PM
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do something!!!

I just had a 383 stroker built and Im leaking from somewhere back there. The builder told me that he used a 1 piece seal. What ever he used, IT LEAKS! Im not sure its from the seal but its pissing me off! So do like these guys say, use some sealer!
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Old 02-28-2008, 05:39 AM
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Quote:
Originally Posted by 383suburban
I just had a 383 stroker built and Im leaking from somewhere back there. The builder told me that he used a 1 piece seal. What ever he used, IT LEAKS! Im not sure its from the seal but its pissing me off! So do like these guys say, use some sealer!
I've got mine done but I havent run her yet so I don't know if she leaks. Mine is a 2-piece seal. I installed the 2 halves "offset" a bit, such that the parting lines do not match up with the parting lines in the block and main cap. I also put a thin film of RTV in "strategic" areas around the rear main cap. You don't want to put it between the main cap and the block, as that will increase bearing clearance, but there are places to use RTV back there where is "can't hurt" to do so. That's what I did. I also put a thin film of it at the ends of the seals such that when the 2 halves meet the ends will be sealed by the RTV. Also remember to lubricate the seal itself with some heavy oil or grease which serves to increase seal life, and act as a sealant.
That's my opinion anyway.

Lee
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Old 09-08-2009, 01:25 PM
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Sorry to open this thread back up but I am also rebuilding a BBC. Half of the people I have talked to say don't oil the rear main seal. Others say to oil the rear main seal. Which one is it?
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Old 09-08-2009, 03:12 PM
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Quote:
Originally Posted by digitaldisorder
Sorry to open this thread back up but I am also rebuilding a BBC. Half of the people I have talked to say don't oil the rear main seal. Others say to oil the rear main seal. Which one is it?
I'm trying to remember what I did. I'm pretty sure I DID NOT oil the rear main seal halves. That is to say I did not oil the "outer" portion of the seal - the part that contacts the block. I DID however oil the seal itself, the inner part that contacts the crankshaft.

Remember to offset the parting lines on the 2 seal halves so they do NOT match up with the parting lines on the bearing caps and block.

If I recall. I believe the next day I took a tiny bit of black RTV and worked it around the rear main seal bearing cap just in case there was a leak between the bearing cap and the block that was not enclosed by the oil pan gasket.

Mine works fine with no leaks. But then again, I'm an idiot so consider yourself warned.



Good Luck

Lee
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Old 09-08-2009, 06:24 PM
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I always put just a very, very small drop of RTV on the seal ends where they meet. Offset the parting lines per instructions and coat the crankshaft with oil and you're good to go. I do smear a very light coat of high temp RTV on the seal seat. Most important is to make sure you install the seal correctly. You can put them in backwards and they will leak like a faucet.
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Old 02-22-2013, 05:16 PM
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rtv sealant and seal question

Rear seal, the flat side faces in towards engine.correct? Also, what is the part # of the sealant everone uses? Thanks Dana
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Old 02-22-2013, 05:51 PM
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Quote:
Originally Posted by 39chevy View Post
Rear seal, the flat side faces in towards engine.correct? Also, what is the part # of the sealant everone uses? Thanks Dana
Here are some pictures. Just use a high temp RTV (red or black) Permatex
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