What is better performance wise, 289 Closed Chamber or GT40 heads? I can get GT40's a good deal but want to know what I can get more performance and HP out of. I am planning on porting and polishing them either way I go.

I would recommend getting a set of heads off of a late 80s truck or van 302. These are the high performance heads put on GT Mustangs in the late 80s, but should be much cheaper. I wouldn't even bother porting and polishing in a van. If I understand head flow correctly, in a heavy vehicle that turns low RPMs, you want stock size port to increase port velocity.

What Reed is referring to would be E7 (E7TE) heads. They are very popular with the Crown Victoria crowd (also heavy vehicles!). The GT40/GT40P heads are acknowledged as better performers, though. They came from the factory on Explorers and Mountaineers, which also need a good bottom end.

Thanks for correcting me! I know just enough about Fords to be dangerous, but not enough to be an expert.

Yeah, I actually was looking at GT40's off an explorer. I think the years were 1996-1997 GT40's and about 1998-2001 was GT40P's

Good info here: http://www.302w.com/Forums/forums/default.aspx

Hey Twisted!! The GT-40P Heads have a different spark plug angle then all the other small block Heads. Just thought I'd let you know that. Headers?? Don't know where you would find any.
I had a set on a NICE 5.0 and MAC was the only one at the time who had Headers for these heads. You could try the Factory Manifolds from the Explorers, but this is something I've never tried. Good Luck and oh ya.... I LOVE YOUR VAN!!! Later Man, Kev-

Kev's right Twisted, and those factory headers on the explorer are really restrictive do to the confined engine bay. I was lucky enough to change a set when I was still working at the dealer....horrible job.

There's no way I am putting manifolds on this at all lol. I think I'll stick with the E7's for a while. If I did get them off an explorer, I would not get the GT40P's, I would get the GT40's.

Definitely the Gt40, they are comparable to the chevy vortec heads, a high swirl. Meaning better combustion efficiency. Which will equal better power and fuel mileage. In my opinion any head older than 1990 when you can get something newer or aftermarket are throwaway, unless you're doing a budget rebuild.