Pictures of KCR Crate Engines.

[Keithc8]

The reason we have not warrantied rear main leaks is because we do not make the blocks or cranks. This is an area that is machined by the block manufacturer and there is no way for us to re-machine this area. We have done some things in the last few years to help with some of these problems. With the one piece rear main seal on the small block that Ford went to in about 1981 pretty much fixed the small block stuff.
We did not design the FE engine block and it has always been a problem. We mike the machined area and even shim the rear seals some plus we now have come up with some what of a second seal on the FE engine. This has all seamed to help with the FE engine. We can machine the small block for a rear seal if it does not have it but can not do anything with the FE because of the way it is designed.
We oil dye test each engine and we have had a few that checked fine on the dyno and then after install have had a small leaks. I will say with the new things that we are doing the rear seal leaks are less. The aluminum blocks will have a little more problem because of the way the block grows and contracts, but these are much better as well. With as many parts as we handle we might get a bad part from time to time.
I hope everything else is well and maybe there are some tricks that we do not know about these FE rear main seals. Can always learn something.

Thanks, Keith