91TKO'D

Does anyone no what years they put hydraulic roller tappets in instead of flat tappets. and also what is the difference between gt-40p and just gt-40 heads? which one will fit on my 91 gt. and how can i tell the difference? thanks guys

NotchAbove

Gt-40P and GT-40, different valve sizes, you can tell the difference as the P will say P on them stamped. Also the GT40 have 3 bars on the front, the P has 4 bars.

ahittz24

87 and up 5.0 engines have the roller cam setup in them. The GT40 and GT40P's will both fit on your engine but the P's require special headers or header sparkplugs like what accel makes. The P's flow better but have smaller valves that the regular gt40's. The GT40s will fit with no problems let you use any stock or aftermarket headers and net you decent gains in power.

91TKO'D

Do you mean spark plug specailty headers or will my flowteck longtubes i have now fit?

Az_bronco_rob

I think '85 was the first appearance of the roller cam in the Mustang (or in any H.O. motor). Starting in about '87 or '88, most of the fuel injected 5.0's came with a roller cam - H.O. or not. The only exception is in the trucks as I've seen some '89's with the flat tappet cam in it.

The "P" heads require a special header - yours probably won't work. The spark plug comes out almost straight on these heads and the header tube will be in the way unless the tubes bend the other way or come straight out for a good 4 or five inches before they start to make the bend.

mjr46

85-95 roller cam blocks in mustangs....and p's have straight plugs and need specific headers and plug wire mods...gt-40's are a direct bolt on with no mods needed