I am asking this for someone else. What's the deal with a leaking rear main seal on a 454 and what is the cost to fix?

------------------
Short cuts always take longer

1985 28 foot Regal
Dave and Deb Bowers

It is two pieces of braided teflon-impregnated "rope". One is forced into a groove on the rear main bearing cap, the other is forced into a similar groove in the block. They rub against the bearing journal of the crankshaft to keep the pressurized oil from getting out. The engine must be raised a little and the pan removed. Beware of any shop that applies jack pressure on the front pulley or harmonic dampner to do this. Then the rear main cap is removed and its seal replaced. The crank can be lowered a bit by loosening the other main bearing caps and the upper seal removed by driving it out with a brass rod or hardwood dowel. There is a tool that fits into an oil hole in the crank journal that allows you to rotate the crank and force the old seal out and the new one in without lowering the crank. Snap-On or KD, I believe.

If I had the pan off, I would replace the oil pump and Plasti-gage the rod and main bearings with an eye toward possible replacement. Not much more work. Maybe even pull the heads for a valve job and punch the pistons out for a hone and ring job, too. And, oh yeah, add Thorley headers and an Edelbrock Performer manifold while it's apart.

Now, just how bad is that leak?

There are products on the market that are purported to stop leaks.

Bill has it right, but it's not as scary as it seems. It's not for the faint of heart, but a good mechanic should be able to do it in 2-3 hours. A talented shade-tree could do it in a day. A GM dealer with a really experienced wrench may be the best place to have it done... be thankfull it is a "rope"type seal! Any larger diesel will have a lip seal... drop tranny, etc. etc. I'd avoid "leak stop" additives and just fix it.