Originally Posted by motorhead
It'* probably not head gaskets. Some suggested it could be a lower intake gasket failure, but the most common cause is an upper intake plenum failure. If it is an upper plenum failure, you will want to replace the lower manifold gaskets anyways because they are not too far behind and it'* a lot easier to do them durring an upper plenum replacement.
If this is what the problem turns out to be, make sure you update the lower manifold stove pipe by one of various ways.
while you are right on the Upper intake failure on the NA cars....the poster would have a difficult time having this problem because his car is supercharged......
do the lower gaskets with the new metal frame ones