View Full Version : Small Block Chevy rear main seal
fichtman
11-22-2009, 06:25 PM
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.......
curtisreed
11-22-2009, 06:48 PM
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
fichtman
11-22-2009, 06:55 PM
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.
curtisreed
11-23-2009, 04:22 AM
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
DRTRCR22
11-24-2009, 10:18 AM
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
DRTRCR22
11-24-2009, 10:19 AM
or UNDERSIZE as some may call it... :roll:
Jim
FullTimeRacing
11-24-2009, 11:47 AM
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:
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!!!!!!!!!!!!
curtisreed
11-24-2009, 04:19 PM
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
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 :D
cepx111
11-24-2009, 08:45 PM
Rotating the seal is just insurance.
I never rotated them before mine started leaking on my 496, shortly after the build I might add.
I didnt wanna go there again as it was a major pain in the a ss to do soooo.... when I put the new seal in, I rotated it.
It hasn't dripped a drop since.
hollowayshotrods
11-25-2009, 03:25 AM
Hink,
Maybe it is time to work on the arrogance problem since you have all the motor knowledge you need. Afterall, it is the light you cast yourself in since you couldn't take Curtis having a little fun.
BTW, I rotate mine too.......No leaks......
Yes, YOU MUST BE LUCKY!!!!
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 :D
curtisreed
11-25-2009, 04:26 AM
Rudy,
I don't think Carl meant to be arrogant. I have read a bunch of stuff he has posted before and I do believe he got the sarcasm in my post. I believe his post both backs up his point for people who are less knowledgable about engines and in the end jabs me a little. He is a pretty busy guy so maybe it came off wrong to some people.
Curtis
suicidebomb
11-25-2009, 04:49 AM
Well, as usual I'm doin it the wrong way :lol:
hollowayshotrods
11-25-2009, 05:07 AM
Curtis,
Thanks for letting me know. I do understand what you are saying, I have a buddy the same way,,means no harm, just comes off the wrong way sometimes. I just took it as him saying we are all wrong and he is right because he does it for a living. I have to assume out of ALL the engines he has built, none have ever leaked out of the rear main, that is very difficult for me to believe.
Anyway, hope you and your family have a great Thanksgiving, as usual giving RA some thought around this time of year. Glad to hear he is in the states training, hope you get to see him for Thanksgiving.
Hink,
Don't take it personal, just giving my opinion of what I read and how I decipher its' intended meaning to the reader. Happy Thanksgiving to you and your family as well.
Rudy,
I don't think Carl meant to be arrogant. I have read a bunch of stuff he has posted before and I do believe he got the sarcasm in my post. I believe his post both backs up his point for people who are less knowledgable about engines and in the end jabs me a little. He is a pretty busy guy so maybe it came off wrong to some people.
Curtis
Hink,
Maybe it is time to work on the arrogance problem since you have all the motor knowledge you need. Afterall, it is the light you cast yourself in since you couldn't take Curtis having a little fun.
BTW, I rotate mine too.......No leaks......
Yes, YOU MUST BE LUCKY!!!!
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 :D
Interesting as I talk to a shop this morning that does alot performance engines and he got an engine in a while ago for circle track application that always had a small leak and when the guy rotated the seal and set the cap in place it pealed the back of the seal off which was piled up between the cap and the block.
Its pretty hard to use the plastic installation tool with the seal rotated when your setting the cap on.
FWIW he also does not rotate the seal either.
Think about !!!!!!!!!!!!!!!!!!!!!!!!
zipper06
11-25-2009, 07:29 AM
Intresting thread, i've never rotated the seals either. Most of the blown eniges i've built seem to leak a little, i just chalk it up to blow by. The only other ones i've had trouble with are a line bored GM 400 blk, i started putting a .030 alum shim under the seal top and bottom and solved those problems. I do use a little silicone at the parting lines.
JMO
Zip.
DRTRCR22
11-25-2009, 06:08 PM
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.
Ooooops, I am wrong, sorry... I was thinking of 400 blocks, my bad...
I have a Dart Little M 400 main block that was lined bored, and I had to use a special undersize seal because of the line bore. Mine is a 388 using a 3.625 stroke with 4.125 bore and 6" rods, so I guess when i read 383 I was thinking 400 block mains...?