Rear Main Seal - Seal Recommendation

[Harry S.]

Time to fix the leak before I do the garage floor. This is for a 1963 300hp 327.

I see GM 10121044, Fel-Pro 2900 and Mahle JV1627. Since they range in price on eBay from $4.00 to $47.00, what is the recommendation?

I found this, is the sealant necessary??

sealleak3_5c9233f0afbdb1ed128c4aa2af8689d0491feb7a.jpg

[Joe L.]

Re: Rear Main Seal - Seal Recommendation

Time to fix the leak before I do the garage floor. This is for a 1963 300hp 327.

I see GM 10121044, Fel-Pro 2900 and Mahle JV1627. Since they range in price on eBay from $4.00 to $47.00, what is the recommendation?

I found this, is the sealant necessary??

[ATTACH=CONFIG]97733[/ATTACH]

Harry------

I have experience only with the GM #10121044 and the Fel-Pro 2912. Both of these are identical. In fact, I have used Fel-Pro 2912 which had the GM part number embossed on them so that kind of confirms that both are the same. These are both fluroelastomer seals and are the best out there. These are the seals I use and recommend. The Mahle might be equivalent but I have no experience with it.

The Fel-Pro 2900 is a standard silicone seal, like the obsolete GM #473424. When it comes to rear main seals, I want to use the absolute best available. That's why I recommend the above.

The sealant in the areas shown on your photo is ABSOLUTELY 100% NECESSARY. Disregard this instruction or do it improperly and you WILL HAVE a leak.

Some folks like to "offset" the seal halves. That might be OK but I've not had problems installing the seal ends flush with the block and bearing cap.

One more thing: you MUST ensure that you do not have wear on the crankshaft seal surface. This usually appears as a very slight groove where the lip of the seal contacts the crankshaft. If there is wear, then you must obtain a seal with an off-set lip which contacts a non-worn area of the crank's seal surface. If you don't do this, you WILL HAVE a leak.

[Harry S.]

Re: Rear Main Seal - Seal Recommendation

Joe, what sealant do you recommend.

Stay Safe

[Joe L.]

Re: Rear Main Seal - Seal Recommendation

Joe, what sealant do you recommend.

Stay Safe

Harry------


What I use is a real old-fashioned, hardening type sealer----Indian Head. However, I might change in the future (assuming I ever build another engine) to an oil resistant RTV like Permatex Ultra Black.

[Harry S.]

Re: Rear Main Seal - Seal Recommendation

Joe, thank you.

Stay safe and travel well!

[Edward J.]

[Mark E.]

Re: Rear Main Seal - Seal Recommendation

Use an anaerobic flange sealant designed for this purpose. The tolerance is too tight for RTV.

[Edward D.]

Re: Rear Main Seal - Seal Recommendation

Agree with Mark, use Permatex anaerobic sealant #51813. It only sets up hard in the absence of oxygen making it easier to work with than air cured RTV. Don't forget to use the little shoehorn that comes with the seal when installing the upper half, there is a good reason for using it so you don't shear off the seal back bead when installing . For this reason, also agree with Joe in that you should setup seals flush and not offset as there is a very good chance you will shear the back bead on the 1/4" of the bottom half that is sticking up when you install. Don't put any sealant on the ends of the new seal, they are already pretreated with an adhesive and will bond together when the lower bearing cap is installed. Keep them clean though, don't get any oils on them, that includes finger oils, use dry nitrile gloves when installing upper half.