Oil in plenum

Hi all,

I finally tore my heads down yesterday for a head gasket job, and when I took the upper plenum off a bunch of oil came out. What causes this? Bad PCV valve? Also where do the gaskets usually go out on these (96' 3100 btw)? It seems like both I've ripped into had it by cylinder no. 1. Is that how they all seem to be?

Thanks!

A leaking intake gasket can admit oil into the plenum, as well as a malfunctioning PCV system, or a really worn set of rings (blowby). Loading the engine before it is at normal operatign temperature can also cause this, as well as a lot of unnecessary and avoidable wear.