1967 With 383 Stroker Motor blowing out oil everywhere??

[Herb E.]

Please help. I have a 1967 Corvette with a 350ci, stroked to 383ci/425hp. I recently installed valve covers and intake manifold of the type used on the 1969 Z28/LT1 Camaros. I connected the passenger side breather hole in the valve cover to the air cleaner, and the driver side breather hole to a PVC valve into the back of the carburator. Motor runs very strong, however, it's blowing oil out just about everywhere (front and back of oil pan, front and back of intake manifold, and around the valve covers). I removed the chrome oil pan and front cover and installed the original type painted oil pan and front cover. Still pushing out oil. I removed the PVC valve and installed just an oil breather and left the passenger side valve cover connected to the air cleaner. Still leaking oil at rear of pan. I'm in the process of replacing the rear main oil seal. Does anyone know why the PVC valve system doesn't relieve the crankcase pressure? When measuring the crankcase pressure with a pressure gage, it reads about 5psi. Someone is telling me that 383's run high crankcase pressure. They are also suggessting that the rings aren't installed properly or are defective. I'm not showing any burning oil out the side pipes. Any suggesstions?.....Herb

[Dale M.]

Re: 1967 With 383 Stroker Motor blowing out oil everywhere??

I can not supply any direct informaiton for a 383 stroker motor. From my racing background, pressure in the pan is caused by gasses from the combusions of the engine going around the rings/pistons. In racing engines, we left a lot of clearance for the pistons and the end-gap of the rings. We ran a supercharged engine and had to address crankcase pressure. I would first suggest you perform a compression check of your engine. A Leak-Down compression check is better at finding the actual problem. I would also suggest that you put a little oil in each cylinder and recheck the pressure. This is a method to determine if the leakage is from the rings. I may be that your engine has been set up with a lot of clearance and that nothing is wrong and you need some better method of getting the pressure out of the pan and not blowing out your other gaskets. How much do you know about the build of your engine? Is it for street or racing. What is the compression ratio? Hope some of this may help.

[William C.]

Re: 1967 With 383 Stroker Motor blowing out oil everywhere??

Have you run a lesakdown test on the engine? What did you have and what results before the changes you described?