several gt-40p questions

Daniel50 said:

I am really excited i just ordered my first set of heads ever for my mustang. i ordered the gt-40p's from tristate cylinder head.

head specs:
60cc Combustion Chamber
Pedastall Type Rockers Used
Positive Oil Control Seals
5 Angle Valve Job
Stainless 1 Piece Swirl-Polished Under-Cut Stems 1.940” Intake Valves
Stainless 1 Piece Swirl-Polished Under-Cut Stems 1.540” Exhaust Valves
AWSF-32C Spark Plug
Springs Good to .550” Lift, (Hyd. Roller) *check cam manufactures specs for compatibility*
(129 psi @ 1.800” / 280 psi @ 1.300”)

questions:
1. will mac long tubes fit these?
2. are these smog legal?
3. which spark plug to use with these
4. worth porting?
5. stock pushrods work?
6. these better than regular gt-40's?

Click to expand...

GT40P's stock have 1.84/1.46 valves and 59cc chambers. They do flow a little better than GT40's and yes they are smog legal as they were used on some explorers. Stock pushrods work yes and as for headers GT40P's require special headers because of their spark plug angle. AWSF-32C Spark Plug. Normally header manufacturers state whether or not they fit GT40P heads.

Daniel50 said:

questions:
1. will mac long tubes fit these?
2. are these smog legal?
3. which spark plug to use with these
4. worth porting?
5. stock pushrods work?
6. these better than regular gt-40's?

Click to expand...

answers:
1. MAC long tubes will fit, however you may need 90° spark plug boots and a cut down socket for spark plug clearance/accessibility. The bolt pattern on the heads is the same as the factory E7's.
2. Technically, they're not smog legal on a Mustang. The Explorer/Mountaineer used an external EGR system, versus the Mustang using the EGR passage in the heads. A competent machine shop should be able to drill the smog passage in the heads to utilize the factory EGR system. Tristate Cylinder Head would probably do it for you, since they have a full-service machine shop in-house.
3. Pick up some plugs for an Explorer/Mountaineer and you should be set.
4. They're definitely worth porting, and can be made to flow quite well. They can flow enough to make 300RWHP, which is right there in TFS/AFR territory.
5. With any major change, you should pick up a pushrod length checker, so you can verify that you'll keep the correct geometry. It wouldn't cost a thing to try and obtain the correct geometry with the factory pushrods, so give it a shot.
6. They're a little better than the original GT40 iron heads because of the revised combustion chamber design, which allowed higher flow with a smaller exhaust valve. With equal work done on either, it would probably be a driver's race if everything else was equal between cars.

Congrats on picking them up. I had looked into it at one time, and even have a set of bare GT40P heads sitting in my garage that I'm planning on selling since I decided to go with the Twisted Wedge heads instead, but I don't think you can go wrong with some "P" heads on a mild street build.

I make 302/324 with my ported gt40p's and e cam combo, so I would say the port work is a go.

Hey Daniel I have those same heads on my 89, the torque is alot better versus stock heads. As for the pushrods I used my stock ones with no problem. I have found that I can't run 87 octane it spark knocks to bad. For the plugs just ask for ones to fit 97-98 explorer v-8's.