Sbc Dart SHP rear main leaks

[MELWAY]

What rear main seals is everyone using and what is your install procedure

I have been building sbc for over 20 years and never has problems no matter what seals I ran

Now days I pretty much only build dart block engines and mostly shp

Last few years I have 1 out of 2 leak on dyno
I have tried ever seal I can get my hands on
The felpro blue 2900 has been the most successful the last 12 months. But I have an engine this week that pisses oil out when hot. First tried mahle grey and now fel pro blue. Both leak baddd driving me crazy

[KnightEngines]

Brown felpro high vac seals are good.
But yeah, I've had a couple of weeping chev seals lately, found one had a distorted lip at the joint.

[jdperform]

We take a piece of rubber bout 1/8 thick x 1” x 4” with bout .1/8 hole in middle then fold it around the oil drainback slot on rear cap. Use a rubber tip blow gun and air up the drainback slot and check the seal with soap bubbles. Easier with 2 people but can be done by yourself. We check as soon as we install rear cap and even before the other 4 caps. Seems crude but this procedure has saved us many many hours of removing pan etc.

[Tartilla]

If this is a more recent factor, is there something wrong with the SHP block & rear main cap?

I don't really like the idea of a 50% chance of leaking oil, even when installed correctly.

[MELWAY]

If this is a more recent factor, is there something wrong with the SHP block & rear main cap?

I don't really like the idea of a 50% chance of leaking oil, even when installed correctly.

I feel that the SHP cap has less slot area than a stock chev oem cap and could possibly be holding up too much oil in seal area.. after trying several different seals in this last engine
I milled the slot area to double its size. Hopefully this might fix it

I’m interested to hear if others have had rear main issues with SHP blocks

[RTR-1]

Are you having problems with 350 or 400 main blocks? Or both?

[MELWAY]

Are you having problems with 350 or 400 main blocks? Or both?

I pretty much only build 350 main blocks

[cad]

Has anyone resolved this? Since off the dyno, my 2pc rear main seal leaks. Im about to pull my SHP SBC out for an oil pressure loss issue and will be pulling the crank.

Thanks
Clark

[Steve K]

There is a different seal for this block. had the same issue and my engine builder replaced the seal with the correct one and no leaks. Standard GM seal work. Don't know the part number but the GM seal was blue and the seal that works is red if memory serves correct. This is a 400 block

[Dave B]

Is the measurement where seal rides correct? Giving correct amount of crush? I have saw couple blocks where tolerance was on big side .003 near parting line and .0045 in center. As that don't look terrible when on engine stand , it will be even worse hot. I have fixed several blocks after guys cut cap a bunch to get it align bored. I talk to allot of engine builders who don't even measure this area.

[cad]

There is a different seal for this block. had the same issue and my engine builder replaced the seal with the correct one and no leaks. Standard GM seal work. Don't know the part number but the GM seal was blue and the seal that works is red if memory serves correct. This is a 400 block

Mine is the 350 mains block.

[Steve K]

Maybe a call to Dart would help

[Dave B]

There is a different seal for this block. had the same issue and my engine builder replaced the seal with the correct one and no leaks. Standard GM seal work. Don't know the part number but the GM seal was blue and the seal that works is red if memory serves correct. This is a 400 block

Mine is the 350 mains block.

Again have you verified block dimension is correct for the seal ? Does your crank measure right where seal lip rides? Sometimes this area on crank can have a spot on it and turning seal other way will fix it. If all measurements are correct 99.99 percent of seals will do there job. I do my personal rear seal area different than anyone else's that I have saw. I'm not gona try and explain it because done incorrectly it will be a problem. I never offset my seals either. The way I do mine seal sits in housing with parting lines same area as cap and block. I can't remember a rear seal leak in the last 30 plus yrs on 100s of sbc and bbc setups.

[houser45]

Try this, cut a .010” or .015” thick out of bulk gasket paper just narrow enough to fit behind the seal on both halves the full length of the seal. Putting more press on the seal. Line up the parting lines directly at the main cap, use light amount of silicone behind the seal.

[Dave B]

^^^^ That's fine if dimensions wrong and that is needed but again measure the area and know what the problem is, don't guess. That's why he is having problems because he is guessing or blindly hoping. Rear main seal is not 5 min fix if you guess wrong!! This stuff ain't rocket science but allot of you try to make it be. If your getting shingles for your house, do you measure to see what you need or go to the store 23 times until you have enough? If dimension is wrong side of tolerance and you shim it, you will wipe out seal from too much pressure and friction