Rear main shims and leaking oil
 

I am getting ready to finally asemble my babbitt style engine after washing it and painting the block (and a lot of other things). I have already used Timesaver to lap in the mains and rods. The Timesaver really worked well by the way. The bearing contact is virtually 100% and very low crankshaft drag at .001 clearance. Using Timesaver is a fairly long process as there are 4 different grades of Timesaver that needs to be used - course, medium, fine and extra fine. Anyway, I, like probably everyone else wants to eliminate or at the very least minimize oil leeks from the rear main. The main (pardon the pun) concern I have is will oil leak through the layers of shims or between the shims and the block and/or main bearing cap? Is there a need to use a very thin layer of Permatex or silicon between or around the outer edges of the shims/cap/block? The engine is a stock engine with the original rear seal and standard head. After all the work I have done on the car, I don't want oil leaks or at least keep them to a bear minimum. Any suggestions would be appreciated.

Re: Rear main shims and leaking oil
 

if you have a rear main leak , it will most likely be thru the bearing , as in to lose . set it tight . should not leak thru shims ..................... steve

Re: Rear main shims and leaking oil
 

Rather than Permatex or a Silicone type sealer, I would use an Anerobic sealer that is used as a sealer between metal components not requiring gaskets. Available at most jobber supply stores such as NAPA etc. Hope you lapped the rear main bearing cap good on a slab of granite.

Re: Rear main shims and leaking oil
 

I use a liquid from Cat.

Re: Rear main shims and leaking oil
 

Won't anything you put between shims change the tightness of the bearing. I'm thinking if it's in there it has thickness.

Re: Rear main shims and leaking oil
 

I just talked to Herm Kohnke in Iowa that rebuild A engines and he said the very thin coating wont change the thickness. He said that oil can seep out between the shims, cap and block. Probably not very much oil would leak out, but I would rather have none leaking out if possible. I used 150 grit sandpaper on a table saw or plate glass to make sure the caps are perfectly flat. Thanks for the advice so far.
Rusty Nelson

Re: Rear main shims and leaking oil
 

You are putting a "VERY" thin coat on. I will act like the binder that holds the shim pack together. You are not looking to have it squeeze out, only to fill the voids in the castings. We use the Anerobic sealer.

Re: Rear main shims and leaking oil
 

Not heard this mentioned above, but isn't it also important to tuck the shims up against the crank journal to close that gap.

Re: Rear main shims and leaking oil
 

Russ/40,
Yes it is important, especially the rear main.
Rusty Nelson

Re: Rear main shims and leaking oil
 

It would sure help, if we all were able to get shim packs that had proper tab shape and fit. "Wish with one hand...and spit in the other" and that's what we get.

Re: Rear main shims and leaking oil
 

A properly assembled rear main will not leak (well maybe a drop or two as it should) and does not need sealer. You want some oil on the rear thrust face. Not only should the caps be flat, but the block and "seal" should be dead flat as well. I assume you have cleaned the rear main oil return passage.

Re: Rear main shims and leaking oil
 

WRNDLN, I'm new to Model a's, just recently bought a 29, what is "TIMESAVER"

Thanks, Tony

Re: Rear main shims and leaking oil
 

Additional info here if you have a leak or want to prevent leaks:


http://antiqueenginerebuilding.com/rearleakpfhtml.htm

Re: Rear main shims and leaking oil
 

Weathrmn: I believe it's a type of "lapping" compound, a four step process( different grades). Someone more knowledgable will probably chime in.
paul in CT

Re: Rear main shims and leaking oil
 

1931 flamingo,
I sent Weathrmn a PM about Timesaver. What you posted is correct and I added a lot more. Timesaver is great stuff as far as I am concerned. I believe it will greatly lengthen the time before the bearings will need to be readjusted.
Rusty Nelson