I am going to assume my rear main seal is leaking, have another thread going on this, only 250 miles on new 383. Currrently have a Fel Pro "blue" seal, that came in the gasket rebuild kit.

Looking around I see there are Fel Pro "rubber", "silicone", "viton" and some other makes and compounds.

Whats the most durable for a hi-perf street car? Mark

 

Whatever you had was fine, how it was applied is probably the problem. Fel Pro gaskets are some of the best.

 

I used the "viton" in my 350 a little over a month ago and it has been fine.

 

With that low of hours I'd lean more to an installation issue. There are some tricks to install but these typically work better on the engine stand versus in the car. Mainly rotating the seal slightly so the ends of the seal are offset compared to the cap to block interface. Some times you may need an anaerobic sealer at the cap flange. And a little grease on the seal lip at install helps until start up. Naturally installing the seal in the correct orientation helps too, I'm sure you did that right.
Last would be check that the seal halves don't stick out proud of either the block or cap to much. If so clamping it together would put the seal in a out of round condition. Slice of the extra flush at surface and then rotate slightly in bore to finish off.

Used to install our dyno engines this way for hundreds of leak free hours. Usually testing other components and didn't want this ruining the test.

Stock - Single lip - BS11829 - rubber, Double lip- BS40013 - rubber, Race #2900 - silicone. There is one, #2909 that has a slightly larger OD for align-honed 400 blocks but if your seal bore is larger for some reason this may help. Fits a 2.8406" - 2.815" housing dia and is Viton.

 

Thanks GasketDude. My 350, 1972 original block was align honed and now using an Eagle 383 stroker crank, would this affect my seal?

What is the beter seal..single lip or double lip? Rubber? Silicane? or Viton?
thanks
Mark

 

www.competitionproducts.com, 2 pc viton race #15109HP
just another to consider.

 

Sorry for wait for response, out of town on business, sent you PM.

Part numbers above would work fine for street and mild race. Other materials are typically for high temp race with external oil dry sump pumps and vac situations.

What was the cause? Haven't seen this posted yet.

 

Doing a dye / UV test tomorrow, will post results

 

What oil pan are you using? There's some pans out there that have an incorrect radius at the rear. You can tell because the end gasket isn't squeezed in the middle. I went through this on a BB build and the pan was from Moroso who you'd think knew how to make a Chevy oil pan. After replacing the rear main seal, and still dripping, I learned this lesson (bad pan) the hard way.

Now I have a Milodon pan now and everything is happy.

FWIW.

 

My 383 stroker with an Eagle crank also leaked within days of being carefully assembled by our long time local speed shop. I replaced the seal myself in the car. I just took my time to make sure everything was very clean and dry. I installed a Felpro Viton seal and also offset it with a little lube on the lip as recomended in the above post. Use a small piece of wood like a dowel to push the old seal out so that there is no possibility of scratching the crank. That fixed it, not a drop after that. However I did have some issues with the one piece pan gasket afterward...I had to reseal that also.

 

Did the dye / UV leak test tonight .....looks like it's the pan gasket. Ran the car for only 2 minutes with the dye, which is in synthetic oil, added about 3 1/2 oz. With the light and yellow goggles under the car. The back of the pan was glowing right away. Nothing around the rear main seal. A faint glow on the bottom edge of the cam plug. Nothing on the galley plugs. Nothing on the back of the block or bottom edge.
So I am going to get the Fel Pro 1 piece thin rubber gasket. Which is correct for a 72 with stock pan and front cover.

I would never have believed a leaking pan gasket would cause such a mess... Thanks to eveyone for your help, advice and enccouragement Mark

 

Before you unbutton everything, see if the end gasket is "squeezed" or slightly bulging uniformly throughout the radius.

Again, what pan are you using?

 

Using the stock GM pan. I am assuming its the original pan. Everything else on the car was original...but you never know. Anyway it's not an aftermarket piece. Will have to check to see how the end gaskets look

 

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