SCAT 408 stroker crankshaft rear main seal leak

[wildbill]

I have a 408 I built last fall using a SCAT stroker kit. No rear main leak when I first ran it but starting leaking after a while and continued getting worse. Replaced the rear main about a month ago - worked great for a few weeks but starting to leak again. Used a standard Fel-Pro rubber rear main set both times.

Anybody else had this problem or have any suggestions to get it fixed for good?

Thanks

 

[yellow rose]

How much of the seal is proud when it’s in the FP and block? If you have a block that has been line honed you need to shorten the seal so you have about .005-.-010 and no more. If you have more than that, it will force the seal out of round when you torque the cap down.

 

[wildbill]

As far as I know the block has not been line honed. It was all original when I took it apart the first time. The machine shop didn't think line honing was needed.

I will have to check how far it sticks out of the block when I take it apart again. At least this is in a D100 so I can easily get the pan off with the engine in place!

Thanks

 

[famous bob]

How much of the seal is proud when it’s in the FP and block? If you have a block that has been line honed you need to shorten the seal so you have about .005-.-010 and no more. If you have more than that, it will force the seal out of round when you torque the cap down.

HEY ROSE , SPLAIN THAT A LITTLE BETTER TO ME .
My 440/505 was only changed about .003 , according to the machinist that did it ,
(only took .003 to zero deck it too) > a .005 under timing chain was a ***** to get on, and still is tite to this day .
I have been fighting oil leaks from day one , even replaced the rear main cap with a billet one that fit perfect ----------thanks Bob

 

[yellow rose]

HEY ROSE , SPLAIN THAT A LITTLE BETTER TO ME .
My 440/505 was only changed about .003 , according to the machinist that did it ,
(only took .003 to zero deck it too) > a .005 under timing chain was a ***** to get on, and still is tite to this day .
I have been fighting oil leaks from day one , even replaced the rear main cap with a billet one that fit perfect ----------thanks Bob

When you line hone (or line bore it) you (usually)cut the caps, making the hole smaller and out of round. Then you hone or bore it back to round. Everything is now back to size. Except for the seal channel. It was made smaller, but the process to get everything back to size doesn’t make the seal channel back to size and it’s now smaller.

Now the seal has way too much crush on it, because the ends of the seal are too proud, not only on the cap but on the block. When you crush it that hard, it goes out of round.

The only way I know of to fix it is to shorten the ends of the seal until the seal is not getting its brains crushed out. I do it with a belt sander and just lightly sand down the ends as equally on both sides as I can until the crush is correct.

 

[famous bob]

When you line hone (or line bore it) you (usually)cut the caps, making the hole smaller and out of round. Then you hone or bore it back to round. Everything is now back to size. Except for the seal channel. It was made smaller, but the process to get everything back to size doesn’t make the seal channel back to size and it’s now smaller.

Now the seal has way too much crush on it, because the ends of the seal are too proud, not only on the cap but on the block. When you crush it that hard, it goes out of round.

The only way I know of to fix it is to shorten the ends of the seal until the seal is not getting its brains crushed out. I do it with a belt sander and just lightly sand down the ends as equally on both sides as I can until the crush is correct.

Thanks I thot that was what u were talking about , wanted to make sure . I noticed when I had it apart to install the new aftermatket billet cap , that it was almost flush w/ the block , ( not proud) hardly at all------------if any.

 

[evil66]

Thanks I thot that was what u were talking about , wanted to make sure . I noticed when I had it apart to install the new aftermatket billet cap , that it was almost flush w/ the block , ( not proud) hardly at all------------if any.

Do you have arp main studs?

 

[famous bob]

Do you have arp main studs?

Yes , the rear ones dont hit anything if thats where your going , LOL -bob

 

[evil66]

Yes , the rear ones dont hit anything if thats where your going , LOL -bob

Ok, was just going to mention that a friends 493 had a big rear main leak. They discovered that the arp studs interfered with the main seal carrier just slightly and they had to do some clearancing to get it to sit flush. No more rear main leak after that.

 

[Bighead440]

Ok, was just going to mention that a friends 493 had a big rear main leak. They discovered that the arp studs interfered with the main seal carrier just slightly and they had to do some clearancing to get it to sit flush. No more rear main leak after that.

WOW, I can't believe they didn't catch that! Every time I'm assembling any B-engine with studs, it's a major problem. They give you 12pt nuts to help but they need serious grinding EVERY TIME for me!