Which rear main seal?

[Patrick H.]

OK, I'm preparing to replace the rear main seal on a '72 350 (base motor).


I see that Fel-Pro has a single lip, double lip and an offset lip. All are "listed" for a 72 small block, but I assume that each has different purposes or reasons for use. My "guess" is that the double lip is likely what I need but can anyone confirm this? My reasoning is that double is better than single, and it appears to be made of a better material. I suspect that the offset lip is for certain usage but again can't find specific documentation.

Thanks for any insight.

Patrick

[Terry M.]

Re: Which rear main seal?

The offset is for if there is a grove worn in the crankshaft by the original RMS. Like some axle shafts, it moves the sealing surface to a slightly different part of the shaft so that the offset seal rides on a new surface.

It might be best to have a look at the crankshaft before buying the seal -- so you can determine which seal will best fit your level of wear.

[Jim T.]

Re: Which rear main seal?

When I do my 85 Corvette I am going to use GM #10121044/FELPRO #2912.
I discovered this seal in GM Chevrolet High Performnce catalogs a few years ago. It was described as being used by NASCAR and is made to do the job. It costs more than other seals as well.

[Erv M.]

Re: Which rear main seal?

Rear Main Seal

Just read an interesting article in the current Corvette Restorer by John Bissell regarding the two different rear main seals available for the SBC - Fel-Pro parts #2900 (silicone, blue) and #2912 (fluoroelastomer, red), wherein the author espouses the superiority of the red #2912. Basically the #2900 is old technology and the new #2912 does the job.

Wanted to pass this on. Hope it applies to your application

[Clem Z.]

Re: Which rear main seal?

no matter what seal you use unless you put sealer between the rear main cap and block you will still have a leak. this is shown in the GM engine service manuals

[Edward J.]

Re: Which rear main seal?

Pat, The 2912 Fel Pro Is The Rear Seals I Use In My Shop, A Bit Of Warning On The Sealer Between The Cap And Engine Block ,only A Very- Very Small Quantiy Of Sealant Is Used At The Rear Of The Cap And Must Be Free Of Any Oils.you Dont Want Any Sealer On The Main Bearing When Main Brg. Cap Is Up And Torqued You Can Also Put Alittle Sealer In The Corners Of The Rubber Seals Front And Rear Before You Glue Those Rubber Seals Into Placed -this Helps Seal The Corners Of The Oil Pan ,and When You Get Ready To Remove Upper Portion Of Rear Main Seal They Can Be Stubborn,use A Small Plastic Or Rubber Mallet With A Small Roll Pin Punch A Tap The Rear Seal In Center,the Seal A Metal Rod Molded Into The Seal, Use The Punch To Just Get It Started Then Used A Small Pair Of Needle Nose Vise Grips To Grab Onto The Metal Rod Of The Seal. Hope This Helps, Just Ask If You Run Into Any Problems. Hope This Makes Since Ed