As a gift my wonderfull girlfriend purchased a set of Valve covers and had them powdercoated for my truck. Yeah she a great girl, but doesnt know a whole lot about truck stuff and the way parts dont interchange. Anyway The covers fit perfectly, but upon inspection the covers i pulled off the truck which are original had a few baffles inside each cover. The new covers did not have any baffles at all on the inside. The problem im having is smoking upon start up. It was only noticed after the cover install. It doesnt happen on every start up, maybe 5 or 6 out of 10 starts. Sometime it may sit all night and not smoke on start up and other times it takes only a few minutes. Could it be the baffles inside are letting oil get into the manifold and down to the cylinders?

 

That would be my first guess

 

Are the baffles you are refering to around the pcv valve perhaps? That is the only way a valve cover is going to allow oil into the intake manifold. I am guessing you are getting a lot of splash on the pcv valve, blowing into the intake and coating the runners. Once you stop, the oil will run down and puddle on the valves causing the startup smoke you are seeing.