The Stovebolt Site Forums The Shop Area Engine Shop Help with rear main seal

So we ha e a 48 chevy 216 that came with a leaking rear main seal.we have replaced the rear main now for the 3rd time.it has zero leaks for the first 50 miles then it starts to leak.once the cap is removed we have noticed that the rear main seal has been spun. And is spinning with the crank.any help would greatly be appreciated.

http://store.enginepartscenter.com/chevygmc-216235261-6100-p2459.aspx

That Best Gaskets seal (6100) is considered to be the best, "hands-down".

There have been many discussions here about how to install that seal. Maybe someone will post a few links?

That is the one I have been using.

How did you fit and cut it/them, and, how did you "measure" to cut it/them?

https://www.chevytrucks.org/tech/bobadler-1.htm

However, some people swear by the "cut it/them a little long" technique.

Just like the instructions say to do it

We just installed a Best Gasket seal a few weeks ago- - - - -not enough run time on the engine to definitely say it won't leak, but I'd put a few bucks on the "no leak" option if I were a gambler. There's also a sneaky trick to installing the seal that involves a home-brewed tool to pack it tightly into place. One thing they do with that seal is to include a very small dowel pin that gets inserted in a drilled hole in the cap- - - - -to prevent the seal from spinning! I think they might have solved a problem that's been around for decades!
Jerry

Do not try and pack more seal into the area, just follow the directions and install the anti-rotation pin. I packed more into the slot a Pontiac 455 just like the way we did with the older Fel-pro seals. It was so tight the engine locked up after the 20 minute break-in run. I replaced the seal with a second one and follow the directions this time. The engine is still leak free 7 years now.

We installed it per the best instructions a d tapped the cap,for the dowel and the sucker still spun.i,have installed plenty of them and never had this problem.

Will at least it held on to the crank!

Not sure what to do with it now, maybe a pin in the block and cap.

This is the home made main seal installation tool Jerry is talking about. I will leave it to him to describe.

For a lot of years, GM provided a tool to dealers to pack rope seals into the engine block and the rear main cap. Service manuals used to illustrate its use . It's simply a round piece of metal with a handle that's the same diameter as the seal surface of the crankshaft. I had a junk 4" piston handy that was a bit larger than the stovebolt seal, and a lathe, so I turned it down to 3 7/8" to match the rear crank flange and added a piece of 1/2" round stock for a handle. A simple rolling motion pre-forms the seal in the groove to the exact shape of the crankshaft, then it's cut off according to the procedure recommended by the seal manufacturer. They even provide a small box cutter and trimming guides with the seal. The 1/16" roll pin that's added to the lower seal groove is probably redundant, but we installed it as well.
Jerry

I used the Best seal on both my 216s and they have worked out well. I didn't pin either one. I do lubricate the sealing surface with a thick Lucas product while putting it together. I learned to bring the main bearing clearances down to the minimums to allow the seal to work.

Years ago when I replaced the neoprene rear main oil seals in a 67 Chevy impala straight six.
I had to lowered the rear end of the crankshaft to get the neoprene upper half oil seal in.
Would that tool work on a neoprene upper half oil seal?

Another happy camper with the Best Brand gaskets and seals.
I have a 56 235 engine with an extensive rear main leak that was solved with their 4519S neoprene seal.
Also they have nice pan gaskets too, all available at the filling station.

Jorb, the neoprene seals just slide in no tool needed