Hi, I've got a 1995 Pontiac Firebird Formula. It's currently running a freshly built 383 stroker with stock heads and intake, long tube headers, and the stock 4l60e trans. It's probably got less than 5000 (Five Thousand) miles on it, but it has consumed oil like crazy since I started using it. The compression is great. It has 200psi in the cylinders. It runs very strong. And, it doesn't throw off any codes from the O2 sensors. However, it burns a crazy amount of oil. How much? I can burn through an entire quart in 4 hours of driving, and running it hard. Here's the thing, it isn't smoking from what anyone can tell, except at the moment I hit the throttle hard. And it quickly dissipates. If I drive it like a little old granny, it hardly uses any oil.

At first, I thought it might have something to do with the PCV valve. The inside of the intake and the runners in the heads are coated with oil. However, after completely disconnecting the PCV valve and the fresh air breather pipe, I am still using the same amount of oil under the same circumstances. My sparkplugs aren't full of crud. They actually look pretty good. But, I have oil coating the tops of each piston. So, I know it is getting in.

I've done some other testing that I find puzzling. If I plug the breather hose and rev the engine in park up to 5000rpm, I begin to build up pressure in the crank case. About 8psi. However, that doesn't happen if the breather or the PCV valve are disconnected from the engine, for obvious reasons. However, when driving the car, under heavy load with everything hooked up and operational, I will see a few inches of vacuum in the crank case under heavy load at 4000rpm and above. But that vacuum will quickly dissipate if rpms are below 4000rpm, regardless of still holding the throttle open.

So, I'm stuck in this conundrum:

Am I burning oil because of the PCV system sucking vacuum from the crank case at high rpm? I am doubtful because the oil is still consumed with the PCV system disconnected and the crank case is allowed to vent to the atmosphere.

Is oil getting past the rings and not being scraped off by the oil rings? I'm not sure because I don't have excessive fouling of the plugs, nor am I throwing any codes.

Do I have an internal intake manifold leak to the heads? Not sure, how can I test for that? This go around, I've used silicone sealer around the intake ports and gaskets to attempt to eliminate that possibility.

I'm at a point to where I'm going to put a leak down kit on the engine to see if I can hear any air getting through somewhere.