I'm not too familiar with Chevy's, but if it is like my Ford, I had to vent the valve covers. I have a breather on one side and a PCV on the other. I ran without a PCV and it was blowing oil out of the dipstick. I would turn the engine off and you could hear the air whistling out of the dipstick tube. I hated to punch a whole in my SVO valve covers but I did it anyway, and now there is no more oil spewing about, and no more air whistling through the tube.