Rear main install bbc 2 piece seal......leaking...

[Paul D.]

396 bbc in Nova.... Have Fel-pro 2904 blue silicon seal....heard different stories...does the seal parting line need to offset a little in the block?...also,what is the best sealer or RTV for the ends of the seal and the mating surface at the rearest point of the block & main bearing cap?....pesky little leak messing up shop.....I have the engine out of car,but do not want it invert it......thanx..P..

[Jim D.]

Re: Rear main install bbc 2 piece seal......leaking...

Your picture shows the correct off-set for the seal. I use Permatex Ultra Black RTV as a sealer.

[Joe L.]

Re: Rear main install bbc 2 piece seal......leaking...

396 bbc in Nova.... Have Fel-pro 2904 blue silicon seal....heard different stories...does the seal parting line need to offset a little in the block?...also,what is the best sealer or RTV for the ends of the seal and the mating surface at the rearest point of the block & main bearing cap?....pesky little leak messing up shop.....I have the engine out of car,but do not want it invert it......thanx..P..

Paul------


First of all, I recommend the use of seal Fel Pro 2918 rather than 2904. The 2918 is a Viton seal.

The seal off-set is something that many folks use and recommend. However, this is not something that GM ever recommended or specified in their service procedures.

The sealer should be used only on the areas of the block/cap adjacent to the seal, not on the ends of the seal. The seal ends are pre-treated with an adhesive. The area to be applied sealer is shown in the Chevrolet Service Manual. A thin coating of RTV will work well. If RTV is used, I recommend Permatex Ultra Black for this application.

[Paul D.]

Re: Rear main install bbc 2 piece seal......leaking...

Joe, why is the Viton superior to the silicon seal?....

[Joe L.]

Re: Rear main install bbc 2 piece seal......leaking...

Joe, why is the Viton superior to the silicon seal?....

Paul------


Viton has higher temperature and greater chemical resistance than silicone. It's a much more expensive material and that's why this seal costs about 2-3 times as much as the silicone.

[Mark E.]

Re: Rear main install bbc 2 piece seal......leaking...

I replaced my RMS basically as Joe described- Fel Pro Viton seal, no offset placement as per the FSM. No leaks.

Clean the areas well where the FSM says to apply sealant, and make sure it's dry and free of any residue. I sparingly used anaerobic sealant with good result. I also recommend the one piece Fel pro blue oil pan gasket, without any sealant. Their gasket kit with the plastic retainers makes the job easy.

[Paul D.]

Re: Rear main install bbc 2 piece seal......leaking...

Mark, what brand of sealant did you use?.....

[Mark E.]

Re: Rear main install bbc 2 piece seal......leaking...

Mark, what brand of sealant did you use?.....

Fel-Pro 221. I took time to make sure the sealant surface was clean, dry and free from residue. Brake cleaner works well. Then apply the sealant sparingly as per the instructions only to the area shown in the FSM. Use sparingly to prevent getting sealant on the seal when the main is torqued down.

[Joe C.]

Re: Rear main install bbc 2 piece seal......leaking...

The Viton seal is orange-red in color.