The Stovebolt Site Forums The Shop Area Engine Shop 216 rear main seal

Folks,

Have been doing a bit of reading on the replacement of the rear mainrope seal on the 216, mine is leaking really badly.

I have an engine hoist, I have 4 post car hoist as well, feom what i read you can change the seal without pulling the motor out, anyone actually done this, it is one thing to read about the process another one compleltey talking with someone that has actually done it

Or should I just pull the motor

Thanks

Steve

Hi Steve,
Pulling the motor will be the most likely way to do the work successfully but will of course be the most work overall...but maybe only slightly. I've done this both ways. Doing it with the engine in the vehicle will be messy, irritating, difficult and it may still leak when you've finished. Doing the work with the engine removed will be slightly less messy, also at times irritating, not really as difficult and it may still leak when you've finished. Tough job either way but at least the weather in Perth right now is perfect for this. Good luck! I'd get the Best Gasket rope seal. You probably have better luck with it.

Thanks Jon

When you did it fitted, assuming you just loosened the crank main caps loose so the crank hung down a little, was there any problems re flywheel or clutch etc, or its such a minimal amount of drop?

Correct me if I’m wrong, but wouldn't the tranny limit the amount the crankshaft drops?

There's enough slack created by loosening all the main bearing caps to pull the upper seal out with a big sheet metal screw threaded into it. The tricky part is getting the new seal pulled into the groove over the crankshaft. Lisle Tool Co. used to make a "Chinese Handcuff" tool to pull the new rope seal into place. The success rate for stopping a leak with a new seal was around 50% in most of the shops I've worked in since the late 1950's. There's quite a learning curve involved in getting it right most of the time.
Jerry

You can also make removal and installation a bit easier if you can rotate the crankshaft. Normally you'd need to remove the rod caps and push the pistons up and out of the way. Just remember to replace all rod caps on the proper rods. You will get a bit more leeway if you remove the transmission as Phil mentioned. As Jerry said, there's quite a learning curve.

Before you do all this, there is another way which might work for you. Remove the rear bearing cap and loosen all other main bearing caps. Pull the crank down as much as you can. Then remove the stainless steel stiffener piece from an old style windshield wiper (maybe like this one: https://www.tricoproducts.com/products/factory-performance-wiper-blades/trico-classic) and grind a taper on one end of it...just taper one side. Now remove the rope seal from the lower half of the rear main bearing cap and measure the length of the stainless steel piece you have there...make sure it also just fits into the lower part of the seal groove. Now with the angled part of the taper you ground facing the rope seal, gently guide it in on the back side of the upper main seal. You will need a small hammer to tap it in all the way around. The taper is to keep the piece from digging into the old seal. Once you have it all the way around, replace the rope seal in the lower main bearing cap as per GM instructions, trim it leaving only about 1 to 1.5mm proud at each end and replace the cap pulling the crank up. Tighten all other main caps and say a prayer or three.

Good luck!

It's also important to get the oil clearance on the rear main bearing as close as possible- - - -.0015" is just about perfect. Ignore that ".003 maximum" specification. A wide oil clearance lets the crankshaft bounce up and down on the seal like a sledgehammer and it also lets lots of oil spray out of the journal and overload the seal. Fortunately, a 216 or an early 235 has shim-adjusted main bearings, so the clearance can be tweaked a little.
Jerry