The Stovebolt Site Forums The Shop Area Engine Shop 216 Main Seal Rope Packing

As I've got so much else apart now I thought I'd have a look at the lower half of the main seal that has been leaking a lot.

I'm going to change it for the recommended Best seal but have been practicing putting the Felpro seal from the full gasket set in the groove. I've worked out how to roll it prior to installation but having pressed it on and rerolled it I've got about an 1/8" proud around the half circumference. Does this sound right or am I looking to get it more compressed into the groove somehow?

And a second question if I may. Somewhere away from Stovebolt I read the Best seal has an anti-rotation pin that needs a hole drilling for but don't think I've seen it mentioned on here. Any experience on this for / against?

Thanks.

I made a tool from an old piston to press/roll the rope seal into the groove in both the block and the rear main bearing cap, but the crankshaft was removed and the engine was on an assembly stand when we did that. You could do that with the lower seal half if you're installing the seal in an engine that's still in the vehicle. The diameter of the seal surface is 3 7/8" if you want to make a seal packing tool that diameter. Back in the 1950's most car dealer service departments had similar tools for shaping rope seals.

Yes, when we installed the Best seal in John's 261 we drilled the center of the main bearing cap for the anti-rotate pin.
Jerry

Does the anti-rotate pin come in the Best Gasket kit?

Is it the little pin in this illustration? (also attached below)

I haven't got the seal kit yet but that's what I'm expecting Tim.

Thanks Jerry, I'd seen a video of someone using a Kent-Moore tool as you describe using your machined piston. Having not done one before (on anything but a stove door) I'm just not sure how much of the seal should end up proud prior to installation of the bearing cap back in the block? I'm assuming its got to be proud of the metal surface ready to be squashed as the bolts tighten?

No, you need to trim the seal flush with (but not below) the cap and the block. The Best Gasket seal "grows" a little as it's compressed, and it will either bind the crankshaft or some of the seal fibers will creep between the cap and the block and cause the oil clearance on the bearing to be excessive. Some people have experienced very tight turning of the crankshaft or even locking it up if the seal is not trimmed flush. The Best Gasket kit comes with a stainless steel shim that protects the crankshaft from being damaged, and a razor-sharp box cutter type knife for trimming the seal after it's installed. I like to use a little brush-on non hardening sealer like Permatex Super 300 between the cap and the block to prevent any seepage of oil between the two sections of the seal. When installing the anti-rotate pin, be sure it does not protrude far enough into the seal groove to score the crankshaft!
Jerry

Thanks Jerry, that makes how to install the Best and finish it clear. After all I've read, I don't think I'd be trying the job if the current leak didn't seem so big - hopefully I can't make it worse even with beginners skill level.
What my inexperience of these seals doesn't tell me is how rammed into the groove the seal should be along its length (as opposed to poking out at the ends) On my test piece I've got about 1/8" of the rope poking out proud along the length of half circle of the groove. When you use your piston to roll / press the seal along its length how close to flush do you get along the length of the seal?
Thanks for your patience!
Keith

That sounds about right, as the seal rope will have a tendency to spread out to the front and rear as the bolts are tightened. I've also found that it helps to turn the crankshaft back and forth a little as the main bearing cap is tightened. If I recall correctly, there is about a 1/16" gap between the seal area of the crankshaft and the block, and also the main bearing cap, so the seal does not need to compress all the way to the metal.
Jerry

Thanks Jerry, that's given me more confidence to proceed!!

Keith

I have used a lot of Best Gasket seals in Pontiac's. This is different material then Fel-pro so follow the directions from Best. I lay the seal in the block and firmly push it in the groove, then use the weight of the crank to form it. I then remove the crank, pull the seal out and place the formed seal in to the cap then add the second piece back into the block. Be sure the bearings are in place. I then trim the ends following the directions with the seal. I don't use the anti-rotation pins they give. I've installed at least 15 of them and have not had a seep or drip yet.

" I like to use a little brush-on non hardening sealer like Permatex Super 300 between the cap and the block to prevent any seepage of oil between the two sections of the seal."

Very important, this step should not be skipped, it makes the difference.

3 or 5 years ago I posted an image of a rear main cap I came across in which somebody had drilled 6 holes and set pins with small slot-like protrusions (to keep the rope seal from turning. In the close-up shot I was able to show 3 of those pins. Whoever did this went to a lot of work. The image is attached.

In that image, above the modified one is a normal one with no modification.

In 60+ years of working on engines of all types with rope seals, I can't remember ever seeing a seal that spun in the groove it was installed in. Maybe the new design ones without the asbestos are different?
Jerry

Jerry I've seen some on disassembly in which the two ends of the rope seal had separated. But I always figured what caused that was somebody had installed the rope seal incorrectly to begin with. Those engines by the way showed evidence of dripping pretty sincerely. But in 56 years I've never seen one spin in the groove, either.

Thanks everyone for the extra info. It'll be a while to get the seal sent over here but I'll let you know how I get on.