I have a 1997 Monte Carlo it has 184k it had a long block installed by the dealer at 130k by the previous/original owner which I am friends with and trust. I did a pressure test and have a slight coolant leak at the back of the intake manifold. This started a couple of months ago but was slight enough I was still let my son use to go to school and football practice with no more than 5 mile a day. Now it looks like there is oil in the water but no water in the oil can that happen through the intake manifold? Or am I looking at doing the heads? Thanks for any help in advance!!

 

One other thing it is running a little rough also that is why I am thinking head gaskets also my son said it has never overheated on him but he does not drive very far also.

 

sounds like an intake manifold leak rather than head gasket, i own a 99 chevy lumina and i replaced mine, i had oil in my coolant, but no coolant in my oil, so im pretty sure its possible fo one to mix and the other stay the same, it all depends on where the gasket is leaking from. my car also ran rough before over heating but it would always take 15-20 minutes to overheat.