The Stovebolt Site Forums The Shop Area Engine Shop Rear Main Seal for 216

Jim Carter sells a neoprene rear main seal for the 216. Is it any good? Is it made by Best Gasket?

2 rope seals seem to be available. One is a standard rope seal by Fel-Pro. The other is a rope seal that looks like its impregnated with rubber or something made by Victor Reinz.

Does anyone have any recommendations about these seals or suggestions for other, better brands?

How about flywheels? mine may not be able to be resurfaced.

And while we're at it, my truck is missing the flywheel cover. Look for a salvage one?

BEST Gasket 6100 worked for me!

I see that Jim Carter and filling Station both sell the Best Gasket 6100. It says it's a rope seal. I guess a rubber one is not produced?

What is the difference between the Graph-Tite rope seal and the other brands "improved design?"

How many miles on your rear main seal, Darling?

I've never seen a neoprene seal for a 216 or early 235. The groove for the seal in the late 235 with the rubber seal is narrower and not as deep as the one for the rope, so if a rope is used it will lock up the crankshaft. A neoprene seal in a rope seal groove will not make good contact with the crankshaft and it will leak immediately. Best Gasket is the ONLY rope seal I'll even think about using. When the tree huggers raised such a stink that the asbestos was removed from crankshaft seals, they quit working right. I don't know how Best manages to make theirs work, but they do it somehow.
Jerry

2500 and still dry

I have put plenty of the Best gaskets in Pontiac's, it's the only rope seal that works. You will know when you cut into it, it slices clean and easy, the felpro will fall apart before you get it in the engine. Be sure to follow directions just as Best spells them out.

Does the best gasket seal neoprene seal work well in a later 235?

Try Langdon's Stovebolt... www.langdonsstovebolt.com

ph 586 739-9601

Can't say- - - -I've never used one. Any engines I build in the future are going to be machined for a full circle lip seal, which makes the effectiveness of both of the 2-piece seals a moot point! I made a fixture that allows my cylinder boring bar to be attached to the back of the block to cut the counterbore for the full circle seal in less than an hour.
Jerry

The 2 piece neoprene (actually isn't neoprene but a proprietary compound developed by Fel-Pro) works ok but there are 3 important caveats:
1...make certain your rear bearing clearance is as small as possible. .001 if you can manage that. Part of the challenge is the seal can't keep up with the shaking of the long wobbly crank with only 4 bearings and more clearance worsens this.
2...make absolutely certain the surface on your crank is polished smooth. If you've been using a rope seal and the surface of your crank looks in any way like the attached image, you must polish it or install a Speedi-Sleeve to make it smooth. Otherwise, you have zero hope of that rubber-like seal working for you. You'll just tear it up quickly. Thousands of these were installed by people hoping for an easy fix without ever considering the rope seal often left a terrible surface on that part of the crank and they always failed.
3...when all is polished and you're satisfied your bearing clearance is ok, then make certain you actually have a snug seal to begin with. I usually slip a dollar bill between the crank and the seal and pull it out to judge the seal ability. If you don't, then you'll need to shim the bottom side of the seal until you do have a nice snug seal. And use some non-hardening gasket sealer like Perma-Tex Aviation on it. Once upon a time I would have said to rotate one half of the seal piece in the groove about 1/16 of an inch or so but an old guy I spoke to around 1995 at Fel-Pro told me they stopped telling people to do that. He said their research had shown it didn't really help that much. But...you can do it if it makes you feel better. It will assure both pieces of that gasket will be mated properly at the ends. If you have to shim the back side, only do so up to around .008". Any more than that and you'll have to use a Dremel tool to trim the stiff wire imbedded in the gasket and the gasket itself.

Good info. So…am I correct in assuming the rope style seal is more forgiving than the rubber?

Usually the Speedi-Sleeve you need is 99387 (from 3.873 to 3.879) and it looks like the image below. I've been told by some that the Speedi-Sleeve can be polished after installing, but I've not done that before and since it is only .012" thick, I wouldn't go too far...

I wouldn't say that. In my opinion the spring-backed one-piece seal Jerry uses is the most forgiving of all and will do the best job (assuming like all others it is riding on a smooth surface). That seal (because of its design) can work with more up/down crank movement. I'd put the rubber seal as number 2 if done correctly with a crankshaft which has good clearance. I'd put the rope seal as dead last, particularly if the surface of your crankshaft looks like the image I posted. Six or seven years ago I had the opportunity to see 5 235s that were disassembled by a friend (to scavenge usable parts, basically). Every one of the sealing surfaces of the crankshafts looked like that image I posted (which was taken of the 235 I'm currently using). Horrible stuff. Those rope seals harbor not just oil but acids and humidity. Once the crank gets buggered up, then the crank will shred the rope, ruin the rubber, etc. The old asbestos-laced seals (like the old brake shoes) were a lot tougher and able to stand wear better. Just my 2c worth.

One point about the rope seal...when your crank is banging up/down, it is hammering the rope seal into the groove constantly. And it isn't just the rear bearing...all the main bearings need to be as tight as possible since there are only 4 and motion in others will transmit motion front/back. This is one thing that causes the rope seal not to seal as well. Back in early college days a friend and I had the idea what was needed was something that could be inserted in the middle of that rope seal which would be elastic in nature. In other words, a core that had spring-like ability to keep the rope pushed constantly against the crank surface. But we never did figure out just what it would be...and as far as know neither has anyone else. Once the rope seal gets hammered down and slick from motion, it just won't seal well anymore. Granted this isn't a pressure seal, but the radical angle of the 235 ensures oil will be always present at that area.

Thanks. I'll keep you posted on the developments.

Are you building up an engine from a bare block, or putting a seal in one that's already assembled? If you've got a bare block, it's a one day road trip to my place, where I can machine your block for the full circle seal. The crakkshaft has to be removed and the machining procedure generates a lot of cast iron chips, so it requires a full teardown and a detail cleaning job afterwards.
Jerry

No, this is just a new clutch installation that has opened a can of worms.

I'm probably not going to replace the rear main seal at this time because the leak isn't that bad. Most of the oil down there is/was from the tranny. Trans has been removed and re-sealed and freshened up. Gears removed, new syncros installed, cleaned, etc.

New flywheel will be installed as well.

The Best Gasket neoprene seal was hard to get into my '61 261 but it doesn't leak one drop. I'd guess that it would work on a later-235.