My engine builder is looking for an alternative rear main seal for a 302 GMC.
My engine builder wrote.
Has anyone found a rubber 2 piece or full round seal for these motors? I have had 2 BEST gasket seals leak on me. Any help is appreciated. I'm not blaming Best gasket, never had one fail before. The second one leaked worse than the first.
I heard that FelPro makes one for the 59 block but not before. Any guidance or input is appreciated as removing trans,driveline,clutch,flywheel and dropping the crank didn’t facilitate a repair. Does the front sheet metal, radiator etc have to be completly removed again to remove the front timing cover, harmonic balancer to drop the front main bearing on the crank to help feed another seal?
Lots of work and money so far but need the oil leak fixed . Please help!
Unfortunately, the GMC engine can't be fitted with a full circle lip seal. The flywheel flange is bigger than the seal surface. The Chevy engine has a straight rear flange, so the block can be machined for the lip seal. I've had some degree of success with adding a shim between the rope seal and the block, putting more pressure on the top side of the crankshaft. The same thing can be done with the lower rope- - - -a thin piece of brass shim stock, etc. If the engine is in the vehicle, it's usually possible to lower the crankshaft a few thousandths by loosening all the main bearing bolts and tapping a piece of the thin stainless steel that holds a windshield wiper together between the rope and the block. Then S-L-O-W-L-Y torque the rear main cap a few pounds at a time while rocking the crankshaft back and forth to squeeze the rope into the proper contact with the crankshaft.
If the seal surface on the crank shows any roughness at all, you're probably fighting a losing battle. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
Pdl, how bad was the leak after installation? Was it seeping a little? Was it creating a puddle on the floor?
1950 Chevrolet 3100 (Ol' Roy)
1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)
I heard that FelPro makes one for the 59 block but not before.
1955.2 thru 1960 GMC Master Parts Book shows the same rear seal (2091026) for all 248, 270 and 302 engines. 1939-1954 MPB lists the same part number for all 228/236/248/256/270/302 engines. I don't have listings for first series 1955.
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
If the application requires a rope seal, you need to give up on the Best seal. Its not the companies fault, but they don't work. The reason? Asbestos. The original rope seals were made up with asbestos component. The new Best seals are a fiberglass graphite affair. Kick the bushes hard for an old gasket set for your 302, think like late 70s early 80s at the newest. Keep your fingers crossed the asbestos based rope seal is there and its pliable. If it is, give that a try.
Please try to get your bearing clearance back to specs...which as I recall was .001". That will help. Asbestos laced rear main seals stopped being made by anyone around 1978 (more on that in a moment). AIG and other insurers demanded it...they would not provide insurance for asbestos in any form after and the gasket companies got hammered with self-insured losses. I was part of the AIG staff at that point. The problem was the courts would just start handing out awards the instant they heard the word. Policy language excluding asbestos didn't become standardized until sometime around 1984 or 1985, however...at least as I recall. Many moons and many courtrooms ago...but I promised more. Please see below.
If you can find a rope seal made with asbestos, that will help. It did work better. Interestingly, I've been watching this for a while and today you can buy 3/8" asbestos rope again. You can see here: http://www.wealson.com/dust-free-asbestos-round-rope.html You would have to figure out how to impregnate it with graphite (because that is what it was) but it is available. Also you can get it impregnated with PTFE. (http://www.wealson.com/asbestos-packing-with-ptfe-impregnation.html) You have to deal with China but that isn't nearly as difficult as you might think.
The GMC engine at least has an oil slinger. The 216/235/261 engines don't and in my opinion they should have had one. You can easily add one in those engines by forgetting to remove the lip of the Speedi-Sleeve. The oil that washes over this area isn't under pressure but the flow can be copious and it will work its way out. Also, I use straight 30 weight...and I know, that is a whole other discussion and there will always be some interesting opinions once discussions begin.
Finally if the sealing surface on the crankshaft is rough, you may as well remove the crank and apply a Speedi-Sleeve and some red loctite. Somebody already mentioned this...Jerry maybe or Mike. My experience has been that moisture and acids in the oil will corrode the surface and make it look like the image you see attached. That will never seal properly until you repair it.
Finally I have seen situations (3 or 4) where somebody drilled holes in the block and cap and set cut-off nails there. This was to keep the rope seal from moving at all, although I'm not convinced it really worked. You can see a couple of images of what I've found below.
Good luck!
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
Just curious: I have a 228-302 rear main seal made by a company named Fitzgerald Gaskets. It is in an unopened envelope with their part number and "To replace part No. 2091026" which is GMC's number. The address on the envelope does not have a zip code, which should place it pre-1964. Good chance it has asbestos. I'm keeping it for my 302 if it ever gets finished.
Would you use it?
'57 GMC 102, Original 347 V8, HydraMatic, 3.08 rear gear, added A/C, disk front brakes, HEI, AFB carb, '98 Honda Black Currant paint. T-boned and totaled 10/12 '52 GMC 152 Stake Bed, Original 228, SM420, added A/C, HEI, disk front brakes, '67 Chev 3.55 rear gear. Gets used as a real truck.
Has anyone considered resizing the seal surface on a GMC crankshaft to match up with an existing 2-piece lip seal? Making a permanently-installed outside holder from aluminum to fit the block and main bearing cap shouldn't be difficult for anyone with the unmitigated gall to call himself a "machinist"! Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
