building a new engine for my truck, will be a .030 bored over 302 when put back in, will gt40 heads actually make a significant difference? like to know asap.

 

Like about 20 HP give or take.

 

FYI on a 302 you're better off with home ported E7s or spend a few dollars more for GT40Ps (but Ps need a specific header). Both will out perform box stock GT40 irons.

PLEASE get a cam in there, even a mild Torque/RV style one will be far, far better than the stock Ford unit.

 

Exactly you will see much more power with a cam with which ever GT40's you get. But as was said with the P's you need to get the tuned to headers. An additional cost and to get the best of it you need the cam too. I ran the box gt40's on an old 308 I had in a stang and ditched them for some AFR's. Those were soooo sweet.

John

 

its not a racetruck, just something to get to work, but i figured if im rebuilding it, im gonna do it right. i got a set of cast iron gt40's, im doing headers, intake manifold, and cam. itll do me fine, with my .030 or .040 over bore.

 

.040" causes heating problem on that 302, don't go that far over.

If it's not for anything aside from work, port some stock heads... they'll make more power than stock GT40 irons in low speed torque and total CFM in I&E.