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.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
