What kind of header issues will a guy have with gt40p heads?? Those are what I am planning on using and no one said anything about header issues on them.

 

I think all GT-40 heads require different headers than a normal 351/other small block headers, I know for sure the P's do, but I think the regular GT-40 heads do also, and I have no clue about the GT-40X heads. The P's also have a wierd plug angle or something like that.

 

GT-40P's have a different plug angle than the other heads. The spark plug issue is more frequently discussed on Mustang forums. I've heard everything from having to use short plugs, a combination of straight and angled spark plug wires, to having to unbolt the headers to change plugs.
I don't have any personal experience using them, but I have seen pictures of the heads and they come out almost 90* from the head compared to the angle on which the others sit.
GT-40's are at the normal angle, and I think the GT40-X and others,(GT-303, GT40Y), are as well, but I not 100% sure.
It might be wise to try and match your headers up to a set if possible beforehand to see if and how bad an issue you might have.

 

4-stroke engine does not require back-pressure to function correctly..

 

HOLY OLD THREAD BATMAN!!!!

I don't bother trying to correct people on the back pressure thing anymore. I just assume they mean velocity and move on.