Hi guys, i had a couple of questions regarding the gt40s out of a 93-94 5.0 mustang,im running stock heads on my 289 is this a good up grade?Would i have to change my cam? im running a solid cam (not sure of the lift but its pretty lopey) with solid lifters and 1.6 crane gold roller rockers.I Came across some one with a pair i can get for cheap,letme know what you guys think...thanks
I dunno what you are looking at but the GT40 heads did not come on any HO 5.0... They did come on the Cobra Mustangs, '93-'95 Lightnings and '96 & early '97 Explorers, later Explorers got the GT40P... Both the GT40 & roller rockers would be a good upgrade...
Well I had a pair of gt-40's not the gt40p's and I ported them and then found out that they would drop my compression even more because I have a stock 72 Mav motor
If you use em...Mill the decks to get em down to 58cc's and change the valve springs...You cant use em with your cam, unless its a roller cam. If so, your cam is probably too big for the springs anywhoo.
Good flowing heads. Swap the springs, or put in a roller cam. Still make sure springs match the cam and lift.
X2 on this, but cc the chambers before milling them, The GT40's installed on the Cobra Stangs were milled already before at the factory to get them to 60 cc's. All other GT40 heads are a nominal 64'cc's (+ or - 2 ccs)
I need to disagree, just from experience. I slapped them on and it was a "whole nuther engine!" I had them milled .010 just to make sure they were true and clean on the bottom, not in attempt to improve my chamber size. This was the first pair I slapped on my original block, WITHOUT changing the springs. It really woke the engine up, but it also ate my cam and a couple of lifters after a couple years. When I built up my current engine, I did not mill the heads at all, and still screams like a banshee. But this setup has a larger cam, roller rockers, roller cam, roller lifters, and springs to match. I would use nothing but GT40 heads, unless I upgraded to aluminum AFRs or similar.
is roller the only cam i can run these heads with? can i get away with running my set up if i change the springs?
I run a hydraulic flat tappet cam with my GT40 heads. You just need the appropriate springs for your cam.
You'll have to check that once it assembled. My engine is a 73 block, hyd flat tappet, with E7TE heads, and it was a bit of a pain to get the right length pushrods.
