smokdfsh

Hi, I've read all sorts of past posts regarding real main seal replacement but it seems like pre 1958 motors are a little different in this regard and there was not that much information specific to my car. What was here on the forum were pretty old posts and I'm hoping for some guidance.

I'm replacing the rear main seal on my original 1957 283. The motor is out of the car for clean and paint. The crank is out and I have full access to replace the seal. The seal that I bought is from Corvette Central and replaces the original rope oil seal. From my research it appears that this is my only option other than the original rope seal as Fel-Pro and others don't make one for the older pre-'58 283's. I could be wrong on this.

This seal is two-piece neoprene with the metal support built into the rubber. It's a bit rough in it's casting it doesn't look so good as other seals that I've seen from Fel-Pro. I really hope it works because it would be a pain to change in the future.

My question is this: does it go in with a little bit of oil wiped on the backside so it slips into its spot? It's a really tight fit and it almost seems like this seal is a bit to long by about 1/4".
Should I wipe a little right stuff gasket sealer on the backside where it meets against the block and cap instead of a lubricant? If I do this it will not be able to be replaced without pulling the engine again and I'm questioning whether this seal will actually seal as it doesn't look perfect.

Finally, should I offset the seal mating ends from the cap and block mating surfaces so the all the joints at not in the same place?

Thanks for your help,
Chris

Geralds57

I've used the same seal before and it will help to coat it with oil to help with installation and yes, you need to offset the ends from the cap. I think a quarter inch should do it. I think the seal lip should go in with the angle toward the front of the engine if I remember correctly. I don't remember if I used sealant between the ends or not. I installed mine with the engine still in the car. Mine didn't leak afterwards.

Bluestripe67

It is recommended that just a dab silicone be placed at the outside edge of the main cap as it fits to the block. Dennis

PAmotorman

use a thin layer of non hardening permatex in the area marked with XXX

smokdfsh

Thanks for all of your advise. It is very helpful. I'll offset the seals from the cap and block, light oil on upper seal, maybe a bit of sealant on lower seal and a dab on the block where the xs are shown in the above pictures.

ILBMF

A little oil on the seal lip that touches the crank. Brakleen everything well before hand. I prefer Ultra black silicone.

Thmprr

The only neoprene type replacement seal to use is the BestGasket 3711X,
Several suppliers repackage these as their own.
if the seal pokes out 1/4" one side if the other side is flush, it means the seal is incorrect or the block/cap groove still has old seal remains in it. I have replaced several of these BestGasket Seals and no failures, always "step" the ends 3/8" and ensure the lip faces forward.
While not compulsory, I always use a smear of Right Stuff on the block/cap contact, and always put a smear on the interface at the rear between the block & cap, also ensure the right Stuff fills the chamfer in the cap rebate.

smokdfsh

Thmprr,
Thank you for giving your knowledge. While I can't be sure, it appears the the seal I bought from Corvette Central is the BestGasket seal. It looks the same but did not come in a BestGasket package. It came in a small Zip lock with CC part number and a small diagram on the back about the dirrection of the lip install. The seal is almost 1/4" longer than the grove in the cap or block when placed in. It crushes/squishes down into the cavity when you clamp it all together. It looks like it would work but it would all be pretty tight and when I tested it without the crank installed, the seal distorts a little bit at the connection of its halves. I suspect the crank will keep it all aligned ok.. What do you think, is it the wrong seal? I definitely do not have any old material left in the cavities of cap or block. It is sparkling clean.

I'm new to this and will be installing the seal tomorrow with some help from someone more experienced. I don't totally understand your advice here:

"and always put a smear on the interface at the rear between the block & cap, also ensure the right Stuff fills the chamfer in the cap rebate."

Are you suggesting that in addition to putting the RightStuff sealer on the mating surface of the block and cap as outlined in PAmotorman's picture above, that I also should add it inside the grove of the block and cap that accepts the rear main seal? Wouldn't that lock it in place and require pulling the engine if for some reason it leaked and had to be replaced? If you could try to explain it to me again in layman' terms, I would really appreciate it. I'm just not sure what a "cap chamfer rebate" is.

I do understand the lip of the seal is directional and that the seal joint is to be offset from the cap and block joint.

smokdfsh

Also- the seal that I got from COrvette Central has a stiff wire inside the neoprene material to help hold its shape. This is the right one?

Thmprr

Sorry if I confused you.
It sounds like you have the BestGasket brand.
The chamfer is located on the rear main cap, so when it is torqued into place in the block rebate, there is a tiny triangle shaped passage formed longitudinal to the block center line giving a oil leakage path.
This is stopped by wiping a thin fillet of RightStuff into the block main cap rebate corner and across the block interface at the rear. It also does not hurt to put a small dab on the butt ends of the seals.
There should be no RightStuff in the Seal grooves apart from a slight smear on the seal where it contacts the bottom of the seal groove.
When the cap is torqued up, you should see a small amount of RightStuff squeezed out of the rear of the block main cap joint.

smokdfsh

Wow, thanks Thmprr.
That's very clear and I understand. Just in time too because we should be installing it today.
You help is very much appreciated.
Chris

smokdfsh

Thanks everyone for all the help. The rear main seal installed without a hitch. It slid right into place and the cap clamped up fine. I used all of your advice.
Chris