383 Rear Main Seal

[Robinson D]

Got a good news/bad news phone call just now. The bad news is during the testing of my rebuild, everything is running smooth, except a leak in the rear main seal. The seal was a rope type, so he has now tried a neoprene seal that is supposed to be the best for sealing a difficult area, and it still leaks. Anyone have any experience with new seals acting up? The good news is that with the aluminum intake it reached 560 hp and 600 ft-lbs of torque on the dyno today.

[Richard Calver]

You can't seal a rope seal 383 with the standard neoprene seal that comes in all the kits these days. You have to get a proper 383 rope seal or a seal from another car and cut it to length. The crankshaft on the 383 has a knurled shaft at the seal designed to take a rope seal as was the norm in those days. Later cranks have a central polished area inside the knurling on which the neoprene seal sits and thus seals well, but there’s no way a neoprene seal lip can seal on the knurled surface. Rope seals for the 383 cranks are no longer sold so you will need to hunt around. I found a Ford Falcon rope seal, which is the right thickness and comes graphited, can be cut to suit and fitted (it is longer than required). The other way is to change the crankshaft, as is often done in a rebuild anyway, but that would entail a lot of work now, or else ditch the 383 and get a 440 - again, too much trouble. If you get a rope seal, put gasket goo where the ends butt together. Otherwise, live with the leak.

[Joerg]

http://chucker54.stores.yahoo.net/bilrearmains.html" onclick="window.open(this.href);return false;

Mancini Racing has a very good solution for the rear main seal, much better than the original rope-thing.

Regards

Joerg

[Robinson D]

Thank you, Richard and Joerg. I am a big proponent of gasket goo, going back to my army days and then as a fireman and EMT before that (ah, youth). I have passed the guidance and the link on to the shop this morning. It seems everyone has experience with a 440, but not so much with 383's (I should talk, this is my first one). Hopefully this will be the last issue before we get it off the stand.