The Stovebolt Site Forums The Shop Area Engine Shop Change the rear main bearing seal, but how ?

Hello,

The 235 engine of my 1952 Chevy 3100 leaks oil at the rear main bearing seal. One shop said, that it is necessary to remove the crankshaft and change the front and rear seal. There is no other way to do this if I want a good deal. The other shop said, it is just necessary to remove the rear mean bearing cap, change the lower seal and for the upper seal they have a special tool to change this seal. The first shop will need 16 hours, will remove the engine from the car, remove crankshaft and so on and take for this job $ 1800.-. The second shop says, they will need just 3 hours, will take $ 200,- for the job.

What shall I do ? Is it necessary to remove the crankshaft to change the seal ? Or is there a special tool which allows to change the upper seal without remove the crankshaft ?

Thanks for your help.

Tom

There is a tool called a sneaky pete. It screws into the old seal to get a grip to pull it out. A new seal can then be pulled into place.

If the shop can and will do it for $200, go for it. Will they stand behind their work?

Ah, oh. Thank you. Well it is good question if they would guarantee for their work.
I have seen that there are several seal materials, does the tool work just with the old rope style gasket or also with the modern neoprene seals ? Or is it possible to insert a modern neoprene seal without a tool ?

Tom

Your motor should be able to take either seal. If you can get it done for $200, I would suggest doing that. Success depends on the state of the main bearings. If they are too worn, the new seal will leak too.

I did my 235 years ago and all I did was drop the rear main bearing cap and push the old seal out of the top with a piece of dowel. It was a neoprene seal. I did not lower the crankshaft.
Now here is a trick. When you install the seal stagger it so the butt ends are not in line with the split in the bearing cap. In other words push the top half through so that it hangs out the bottom about 3/8". That will also give you a space at the opposite side in the top. When you put the bottom half of the seal in the main cap stagger it the same amount so in effect a portion of the seal will project into the upper half and you will have a space in the main bearing cap where the extended seal from the top will fit. When it is done there is no gap on the main bearing cap for the oil to leak through. When the oil works its way through the gap between the main bearing cap and upper part it will be met by a seal and the oil will not pass it.
Perhaps a bit difficult to understand as its not easy to describe. A drawing would be worth a 1000 words in this case.

Readers Digest version:

Offset the ends of the seal close to 10:00 and 4:00(or 8 and 2), not at 9 and 3 like the seams of the bearing cap.

With the seal and the cap seams at 9:00 and 3:00, the seal is more likely to leak.

Right, Bill?

i have done the sneaky pete a few times it has allways worked for me. now one other thing to check . plastic gage the main clearance on the bearing some times you have to use a new one and i once had to go .001 under.

as for this stagering the seal ends don't like it. i have built many motors and never had a seal leak and i put them in at 3 and 9 o'clock with a dab of sealent.

yep, its a sneaky pete for the rope seals. I've had one ever since mid 70's and have used it twice with no problems.

Reader's Digest version! Of course! Why could I not have explained it so simply! Thanks!