I was about to blow a hole in the back of my head trying to figure out where this exhaust leak was coming from. It turns out there are 2 holes in the back of my heads blowing out exhaust. I couldn't feel if they were threaded or not due to temp., but the motor is an 87 lincoln roller 302. Anyone know what these holes are for? Thanks - Chris
Those are "Thermactor" ports. Where the old (Lincoln) fresh air pump pumped air into the exhaust ports. Emissions control junk. There are many fixes, but I think the best is to get 2 plugs at your local Ford dealer. Someone posted the exact Ford part number IIRC a while back.
I had the same problem with my gt40 heads so I went to Home Depot and bought a long threaded bolt type thing, cut it, and plugged it. I also put a groove on the plug so I could get it out with a phillips head screwdriver if needed. It only cost me a couple of dollars total.