[Merv and Sharon]

Photos might help Chris. I have pretty much the same motor but with new heads, and so on. Are yours the original Mustang HO heads? I take it the Plenum is still fitted and is any of the old smog pump setup still there? There was a connection for that at the back of the head on that passenger (L) side that needed to be sealed.

It would not run so well with a cracked head ...