Rear Main


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By Cactus - 12 Years Ago
I could not get my rear main to seal on my motor so took it down again and found that the seal is not putting enough pressure on crank. This is a 312 turned to 292 specs. My question is what should the diameter of the crank be at the seal journal? is there any fix if it has been turned down too far?
By PF Arcand - 12 Years Ago
Jan: It's late info for you.. but you should have gone to J. Mummert's site where the correct rear main oil seal journal specs are posted. Also, there is more than one type of seal available. Apparently some seals issued in gasket kits, after the use of Asbestos in them was discontinued, are even more prone to leaks than the originals. I believe Best Gaskets can supply two later types. Hopefully your 312 crank hasn't been ruined!
By Cactus - 12 Years Ago
Thanks, I forgot about Mummert's site, I will give it a try.
By Cactus - 12 Years Ago
I can't find the info I need, but my next question is would this portion of the crank be the same size as the main journals?
By aussiebill - 12 Years Ago
Cactus (5/15/2013)
I can't find the info I need, but my next question is would this portion of the crank be the same size as the main journals?


No, the 272/292 rear seal journal is app 2 .600" dia, while the main bearing journals are app 2. 498".
By Cactus - 12 Years Ago
Thank you Bill, that is what I needed.
By PF Arcand - 12 Years Ago
Jan: The spec on Mummert's site was under Crankshaft Identification. It lists the 272-292 seal journal as 2.620" The 312 seal area is 2.750"