A friend of mine recently bought a '66 289 to build for one of his cars. What are these holes next to the exhaust ports on the heads?? I've never seen anything like this before...
The hole is for a thermactor exhaust system https://www.vintage-mustang.com/thr...lts-protruding-into-the-exhaust-ports.639254/
Okay, so it was a California emissions thing. My '66 289 heads didn't have that. But all the 289 and 302 heads I've seen had a hole in the back of each head, and air injecton openings cast into each exhaust port. So I really don't see the point of that setup...
Those ports started out as a CA thing(I believe '66 was first year) but by '68, std transmission 289 /302 used thermactor. Automatics did not use air injection(at least 49 states), thus had no ports in ends or above spark plugs. By mid/late '70s castings had been revised to locate port into ends of heads.
Depending on what type of driving your friend is planning on, he may want to ditch those for some aftermarket heads. The factory heads are pretty crummy when left as is, especially on the exhaust side.
I just closed mine off. I hear those heads are very low compression and sucky suck. But right now im gonna just plug and use those heads. This is what was in there originally ....
