1969 Pontiac 428 that pours oil from the rear of the engine you used a neopreme seal instead of the rope seal any suggestions?

Answer 1

There is a new graphite rope seal that seems to work well. The original rope seals contained asbestos, and worked well, later asbestos free replacement rope seals did not. The neoprene seals can work well, and offer the advantage of lower drag and a few more horsepower, but are very "installation sensitive". Did you put a thin layer of silicon behind the seal all the way around it? Did you stagger the mating surface so it is not in line with the main cap mating surface? Did you apply a dab of sealent to the mating surfaces? Is the seal facing the right way? Has the block been line bored? Line boring reduces the depth of the channel the seal sits in, and can cause sealing problems. Are the two ends that butt together perfectly flat? Some of the cheaper seals are not. Any little error or imperfect mating surface when installing the Viton neoprene seal will result in a leak, the graphite rope seal is much more forgiving. The graphite rope seal is available from most any of the Pontiac specific engine builders, it is made by Best Gasket Company, and is not the same as the rope seal commonly available from auto part stores. Before you change the rear main seal, make sure that is where the leak is from. Some later Pontiac V8 oil pans had the "three prong" rear oil pan gasket, these are very failure prone, the earlier cork pan gasket (the best), or the "five prong" gasket (good) is far more durable. If the leak is from the pan and not the rear seal an application of "the right stuff" by Mr Gasket will seal nearly any gasket leak. The bad news, as I am sure you already know, to change the rear seal or pan gasket the engine will need to be removed again, or at least raised in the chassis.Another thing to check is that your engine builder installed the screw in oil plugs at the rear of the engine, of course if one of them is missing you will have no oil pressure and a MASSIVE oil leak (think Exxon Valdez). Good Luck.