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Thread: Small Block Chevy rear main seal

  1. #1

    Small Block Chevy rear main seal

    Why does the rear main seal leak on my freshly blt 383 with new Scat 9000 crankshaft.2 piece seal.... Everything new, including Summit 7 quart pan !

    I am mad enough to build a Ford............why why why...........now what ?

    The engine runs like a bandit..........i love it . Advise......................no wisecracks like ' change the seal,whats your problem '

    The friggin thing should not leak...........fel pro seal...............thanks for listening.......

  2. #2
    Senior Member RACING JUNKIE curtisreed's Avatar
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    A few questions to think about and I'm not trying to be smart. Did you rotate the seal so the splits are not lined up with the cap splits, did you use a small amount of sealer on the ends of the seal, are you sure you didn't put it in with the lips facing the wrong direction. Have you done a leak down test to check for bad blowby?

    Curtis

  3. #3

    Rear main seal

    Thanks,..........good questions and points to consider. Yes i did those things....................its got less than 500 miles...............rings not sealed yet...................leak may get better...................not really leaking in military definition..............seeps actually,but disappointing anyway.

  4. #4
    Senior Member RACING JUNKIE curtisreed's Avatar
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    One other thing to consider is how you are handling the blowby. If you are using a pan-e-vac system make sure that the check valves on the headers are not rusted or stuck so that they won't work. On one of our cars we found bad ones and it made a big difference oil leaks and picked up a tad of E.T. This is a 700hp SBC. It is on alcohol so it can have quite a bit of crankcase pressure.

    Curtis

  5. #5
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    Another thing to consider....

    IF your block main journals were line bored during the build, it is common for the rear main seal area to be cleaned up along with an main journals, causing additional clearance not expected from stock rms bore specs.

    This happens frequently and requires a special oversize rear main seal to take up the slack after machining.

    Ask your engine builder about this, and find out of you need one of these oversize rear main seals...

    Jim
    I'm not hatin... I'm just sayin...

  6. #6
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    or UNDERSIZE as some may call it... :roll:
    Jim
    I'm not hatin... I'm just sayin...

  7. #7
    Senior Member DYNO OPERATOR
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    the rear main bore should not change just cause you line bored it,It sits in the chanal. :?: Oh wait it will my bad.

    My crappy hamburger pan leaks ,and that pissed me off. :x

    I got over it when I told myself I had to pull it out. :cry:
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  8. #8
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    Quote Originally Posted by DRTRCR22
    Another thing to consider....

    IF your block main journals were line bored during the build, it is common for the rear main seal area to be cleaned up along with an main journals, causing additional clearance not expected from stock rms bore specs.

    This happens frequently and requires a special oversize rear main seal to take up the slack after machining.

    Ask your engine builder about this, and find out of you need one of these oversize rear main seals...

    Jim
    I have line bore and line honed thousands of 350 block over the years and unless we are putting on a billet rear cap I have never touched the seal area. 400 blocks are a different story!!

    I have never in 38 years of building engines ever offset the rear seal in a block before.

    I MUST BE LUCKY!!!!!!!!!!!!
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  9. #9
    Senior Member RACING JUNKIE curtisreed's Avatar
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    Carl,

    Don't be dispelling the myths and misinformation that some of us hold on to. LOL You have to rotate the seal it said so in Hot Rod when I was a kid. :lol: :lol: Sometimes you do what makes you feel good, you know. I have talked myself into doing worse things. I've never had one leak either.

    Curtis

  10. #10
    Senior Member EXPERT BUILDER
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    Quote Originally Posted by doorracer
    Carl,

    Don't be dispelling the myths and misinformation that some of us hold on to. LOL You have to rotate the seal it said so in Hot Rod when I was a kid. :lol: :lol: Sometimes you do what makes you feel good, you know. I have talked myself into doing worse things. I've never had one leak either.

    Curtis
    We do this for a liveing and never had any problems and GM has done niliions of them and they never seem to have any issues with the amout they have done over the years.

    I have taken dome big name engines apart and they have not rotated the seal either.

    Its hard to beleive you would no more about putting in rear seals then DEI, Roush, Hendricks and RCR and Felpro. Maybe you know something they don't
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