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Old 12-12-2006, 07:46 AM
BMiller
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Unhappy Rear Seal Woes

For some reason, I have yet to figure out, I can't keep my rear seal from leaking. I'm running an old style block with 2-piece rear main. I've replaced the neoprene seal twice and still get a leak (into the bell housing no less). Yes it is installed correctly with notch facing forward and rotated approx. 30 degrees. I'm considering the old rope seal this time (aside from starting over with a newer 1-piece seal block). This was never a problem until a recent rebuild (no change in crank, just seals and bearings). Any help/insight/comments would be greatly appreciated.
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  #2  
Old 12-12-2006, 09:03 AM
Dawson Motorsports
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Bill, I'm not sure which engine your running but I know for the GM's, Felpro makes a seal that is oversize and repositions the seal area on the crank. If you run a Ford, I would think they make one for them also.
Chuck
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Old 12-12-2006, 09:10 AM
BMiller
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Quote:
Originally Posted by Dawson Motorsports
Bill, I'm not sure which engine your running but I know for the GM's, Felpro makes a seal that is oversize and repositions the seal area on the crank. If you run a Ford, I would think they make one for them also.
Chuck
Interesting you mention that because it appears the seal may be too long in circumference and the ends are forcing BDC and TDC away from the crank. In addition, the FWD facing notch is BELOW the cap edge so the oil pressure can't force the lip against the crank.

Anyone know info on oversized FoMoCo rear seal....I've never heard of this. I firgured the old rope seal will expand once it gets oil on it and do the job.
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Old 12-12-2006, 09:34 AM
King Matt
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Was the block line-bored by any chance? What you're describing sounds like the two-piece seal is being crushed into an oval, possibly because the ID of the seal bore has been reduced. The rope seal might be worth a shot.
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  #5  
Old 12-13-2006, 10:19 AM
BMiller
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After further inspection the seal appears to fit as intended. It also appears the leak path is the butt ends of the seal halves, at the lip portion, NOT the portion where the rod resides (I have a picture but too high resolution to post). Could this be a by-product of too high oil pressure? My start idle pressure is ~70psi. <sigh>. I'm going to check crank runout at the sealing surface but doubt the crank is out of round.
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  #6  
Old 12-13-2006, 11:53 AM
Dawson Motorsports
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Bill, you may want to try a goo called gasket eliminator at the butt ends. This product is made by Locktite. It stays flexible throughout a broad temp range and is designed to take up very small abnormalities in o-rings and gaskets.
70 psig at start up isn't bad.
Chuck
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Old 12-13-2006, 12:07 PM
BMiller
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Quote:
Originally Posted by Dawson Motorsports
Bill, you may want to try a goo called gasket eliminator at the butt ends. This product is made by Locktite. It stays flexible throughout a broad temp range and is designed to take up very small abnormalities in o-rings and gaskets.
70 psig at start up isn't bad.
Chuck
Thanks Chuck, I'll see if I can find it. I did not RTV the butt ends in this case as is often recommended. I would be very surprised if the crank is out of round.
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Old 12-13-2006, 04:03 PM
thomas toth thomas toth is offline
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I'm not 100% sure if I remember this right but don't you put a smidge if RTV on the back edge and sides of the rear main cap (between the cap and block)? I'm talking just a hair to stop the leak path. I could be wrong, it may be the fumes from the Brake Clean I have been using. This would have been a question for JB but by now he is probably racing Formula V or something.

Tom
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Old 12-13-2006, 04:13 PM
Dawson Motorsports
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Bill, It's Locktite 518, If I remeber I had to have a large supply house order it in for me. Maybe it was the size and quantity I needed at the time.
Chuck
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Old 12-13-2006, 06:50 PM
BMiller
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Quote:
Originally Posted by thomas toth
I'm not 100% sure if I remember this right but don't you put a smidge if RTV on the back edge and sides of the rear main cap (between the cap and block)? I'm talking just a hair to stop the leak path. I could be wrong, it may be the fumes from the Brake Clean I have been using. This would have been a question for JB but by now he is probably racing Formula V or something.

Tom
Yes, been there done that. No leak from the cap, it is definitely coming from the seal.
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