I went through the vacuum leak with a 440 vehicle I bought. On the way home it started running like crap. I had all I could do to keep it running. Got home and pulled the intake off, the previous owner had installed the aluminum intake without paper gaskets. I installed paper gaskets on either sides of the metal bathtub gasket and it sealed up and ran perfect. I would never install an aluminum intake without the paper gaskets. Cast iron intakes seal just fine with the metal bathtub gaskets. Aluminum, not so much.
I beg to differ. I have a Performer RPM on my low deck stroker. It seals just fine with a bathtub(no paper) that's been reused a couple times w/different manifolds.
I'm wondering if the OP's heads have been cut and the manifold he took off was cut to match while his new intake is not??
