This main seal seems to be a pain in the butt... its the cam driven water pump shaft seal.. the cam drive thru this seal in to the water pump on the LTI engine.. primarily 92-97 Corvette, Camaro & Trans Am etc.

Often the cause of long diagnostic time looking for a electrical type miss - or misses or does not not after warming.. mist is created and stuffing up the optispark...

One per car.