The Stovebolt Site Forums The Shop Area Engine Shop Rear Main Seal blocked by shim?

Hello,

I'm replacing the rear main seal in my '57 235 six cylinder. It was rebuilt not too long ago, but the rear main seal leaks. When I took off the rear cap I found that part of a shim was over the top of the rear main seal, between the two pieces. It appears to be a thin copper shim. Do I need to trim this off for the two pieces of rear main seal to seal properly?
I've never seen this issue before.

http://i156.photobucket.com/albums/t24/vetteman61/IMG_1418.jpg

Thanks,
Brandon

I think you have the wrong seal installed.I believe you should have the wick seal or also known as a rope seal.It looks like you have a neoprene seal that was used staring in 1959. rear main seals

Some others will chime in shortly,lets see what they have to say.

Tim

It is not recommended to use a neoprene seal on a shimmed engine.
The shims will hold the ends apart and leave a gap near the crank.
If you trim the shim around the seal the oil will most likely go through the gap between the seal and shim. If some sealer is applied in that gap it might work.
Your bearing is not looking very good either.

Yes, I'm going to have to replace that rear bearing as well. I had this engine professionally rebuilt and I'm not very happy with what I'm finding, but that was about 3 years ago, even though the engine doesn't have very many miles on it since then.

Brandon

I just called Clevite, the bearing company, and they said that this bearing set has to have a shim set bought with it and each one has to be shimmed for these bearings.

My crank is .002 under, so luckily they still make that, but the local distributor wants around 100 dollars for a set of bearings and I only need one bearing. I can't find one by itself. Also, on these '57 235s each bearing is a different size.

The way my son in law showed me on installing a rope seal is trim the shim so that the rope seal ends can meet when you put the main cap back together as on the instuctions.Also just before you put the main cap on put a dab of # 2 permatix on the two ends so that the gap from having the shim is sealed.Also to much play in the rear main can cause the rope seal to leak also,it pounds the seal out of round.


Pete

Here's what I'm confused on. I've researched this in the past and found that any 235 after 1955 can use a rubber rear main seal. Anything before then must be machined to accept a rubber seal. However, it was my understanding that the '55 and up motors could use a rubber seal because no shim was involved. If I have to add a shim then I wonder if that means I'm no longer able to use a rubber seal.

Brandon

My 55 235 power glide uses shims on the mains only,and I used a rope seal ,the gaskit kit did come with a neoprene seal and a rope seal. Go to a engine rebuilders shop they can order bearings one at a time.

Pete

This is the first time I have heard of a 57 235 with shims. Those bearings come up on Ebay from time to time. You might want to call Kanter's about buying the one bearing.

I would not expect shims on any 1955 second series or later 235. I would check bearing clearances to see if you really need the shims. The shop that did the rebuild may not be use to 235 setups.
I also wonder if they used .002 under bearings on a standard crank making shims necessary to get clearance.

It also looks like the casting is chipped in the middle.I think I would check the rest of the bearings,if it was mine.


Tim

Well, I went to order new bearings from Clevite. You can't order directly from them, so I talked to one of their guys and then I also talked to one of the guys through Nashville Engine parts, and both said that when ordering bearings for a 235 in that year, you have to hand shim each one. I hadn't heard this, but apparently both thought of it as common.
I wasn't aware the full pressure 235s ever had to be shimmed, but apparently so.
The part number for a 1957 235 bearing kit is: MS197P20 and the shim kit is: SM124S.
Apparently there's a better way than using plastigauge so I'm going to have to learn that. At least I don't have to file down the bearings like with babbit.

Brandon

Jackie at Nashville Engine Parts used to be the lead salesman at Grooms Engines before they sold out to a yankee outfit and the quality control went to pieces. I've done business with him for over 30 years. The shims are optional, used as necessary to establish the right main bearing clearance. I like to insert a small piece of shim stock between the bearing shell and the crankshaft, and check the turning effort at the flywheel. When the engine will turn with a slight drag with a .0015 shim under the main bearing, the shim pack between the main cap and the block is about right. Use a check shim about 1/4" wide across the full length of the bearing. Don't forget to remove it after you find the right shim pack! There might be a different shim pack, or none at all, for each individual main bearing. Drop me an IM or an email when you're ready to assemble the engine, and maybe we can get together so I can show you the procedure.

I aviod the "leak at the joint" problem by rolling the seal about 1/4" in the block so the parting line doesn't line up with the place the cap meets the block. Problem solved!
Jerry