VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Neoprene seal conversion

The rear main seal is leaking on my chevy's original 216. I have been told there may be a neoprene conversion kit available that would eliminate the old rope seal. Input would be helpful.

I know of no conversion kit for the rear main. The rope seal will give many miles of service if installed properly.

thanks,
Yes I know of a guy who installed one properly and it sealed properly up to the time he went to a 235. He never got the 235 to seal properly. HA-ha He has stressed to me the operative word is installed "properly"

The neoprene rear main seal is for 1955 and up 235 engines only. Note that when Chevrolet offered this seal for replacement as well as the present Felpro catalog list its application as being for 1955 and up. The oil seal grove in the block and main bearing cap is too deep on the pre 1954 engines and the lip of the seal will not even contact the crankshaft.

There is a company, Beck's Machine & Tool in California (http://www.inliners.org/becks/) that provides a service wherein they re-bore the seal cavity in the rear of the block and rear main cap to accomodate a modern, one-piece, metal-jacketed neoprene lip seal. The sealing surface is on the OD of the flywheel mounting flange on the crankshaft. They say they can do the modification on 1941 and up motors. I'm not sure how they deal with the pre-1948 shimmed main bearing caps, as changing the number of shims would change the effective seal cavity bore diameter.

In any case, the service is probably quite expensive, plus you'd have to ship your block there and back. It appears to be a nice, effective replacement of the original rope seal, but probably not worth the expense to any but a real no-leak fanatic.

Mark

hi there,
the rear main on my 34 is also leaking like a sieve, is there a kit for this model, or what do I do to stop the leak?
Peter

There is no rear main seal in 1934 engines. There are two problems that typically cause excessive oil leakage past rear main bearing. A bearing/crankshaft gap 0.002+" and/or a plug or narrowing of the drain passage in the rear bearing cap.

This has been discussed many times on ChatII as it is a relatively common problem. In one case a machine shop removed most of the slinger that was built into the crankshaft to sling the oil that gets past the seal into the cavity that returns it to the crankcase.

I installed a neoprene rear seals in my 1950. I put a .045" thick nylon tie strap under the seal to bring it out farther. This made the seal (upper and lower ) too long so I ground the down ends using the main bearing cap as a guide.....as the seal has a steel core.

My '34 and '39 had no seals and they were the least leaky of all my cars.

I have just received the latest newsletter from the filling station and guess what? they have a complete explanation of the very problem that I am having with the rear main oil seal leaking like a sieve, so go to this link and read the compete article......... most enlightening indeed.....

http://www.fillingstation.com/newsletters.htm

Peter

Peter,

I just went through that. It turned out the drain hole in the bottom of the slinger groove was full of grease/sludge as well as the passage under the cap. The check ball was even stuck in it. I cleaned that up and the problem appears to be fixed.

Hi there Pat S,
yes I followed your post with great interest and I'm pleased that it is now fixed.
I have only very recently had my car running (driving it up and down the drive) and the leaks, front and rear became evident. Its strange that it did not leak at all when stationary?
I am busy fine tuning everything, hoping that it keeps running for more than 10 mins.
The carbie has been on and off 3 times and I had to reposition the fuel line higher so that the fuel did not evaporate, it ran between the rocker cover and the thermostat... way too close.
I will drop the sump later, once everything is running more smoothly, and I bet I have the same problems as you?

Peter