gt40 heads vs stock

[mustangrfast88]

ok , i am thinking i might have to pull the motor to do some repairs to it. was woundering what the differance in the gt40 heads are over stocks heads because if i have to pull the motor down that for again i am changing the heads and cam and intake.

[Timido]

GT40p Heads and intake 1.7 roller rockers shorty headers stock short block stock cam. My car ran 12.40s and made 250hp to the wheels

[mustangrfast88]

i see thats cool but what is the differance with gt40p heads and just gt40 heads and i planned on putting a e cam and a intake and rockers on the car too and a complete exhaust

[Timido]

gt40p heads are almost the same. Gt40p heads had different spark plug angle but they are very similar. Gt40p heads are usually cheaper and easyier to find than gt40 heads. If you are using shorty headers with gt40p heads they need to be mac or FMS Headers that fit P heads.

Same goes for the Explorer intake and the Cobra intake they are almost the same. I ran both intakes with not much change.

[85_SS_302_Coupe]

I believe there's a combustion chamber difference between the two but i don't remember which is larger and which is smaller. It's not a huge difference either.

[mustangrfast88]

well i got mac shorty headers already so does it matter if i get a set of ps or is it a special shorty header from mac

[mustangrfast88]

well just looked and it is 2 different headers so what is the differance

[Jeff88coupe]

If you have MAC unequal length shorties you maybe able to get them to work with the P heads..but it will be pretty tight it they do. The spark plug angle of the p heads has the plugs stick almost straight out unlike the stock/gt40 heads where they are angled back. I was able to use Mac 1 5/8" lt headers on my old p head combo motor. A stock shortblock with gt40/p heads,e303 size cam, cobra/gt40 intake will make enough power to run mid 12's or better.

[85_SS_302_Coupe]

I've never heard of shorties working....only the Mac full lengths....when you do try to install them, make sure you can get the plug wire on with the headers bolted on. I've heard of guys getting desperate and running them, but different headers might have to be taken OFF just to get the plugs out. Most full lengths work because the primaries come straight out from the head were as a lot of shorties only come out an inch or so before they start bending downward.

For what it's worth, the FMS P-head shorties are very nice headers from what i've heard.

[Timido]

I had the FMS P headers they fit nice and you could get to the plugs very easy.

[5.0calypso93lx]

Tom Moss runs his self ported explorer intake and cleaned up GT40p's and is making 277hp at the wheels. The GT40p heads are better than the regular GT40's:

http://www.allfordmustangs.com/Detailed/630.shtml

[ibstrokin]

Just buy a junkyard explorer motor with low miles, then you dont even have to tear down your engine, and you'll have a better intake.

[Rich]

Just buy a junkyard explorer motor with low miles, then you dont even have to tear down your engine, and you'll have a better intake.

This is exactly what I was able to do. I found a 2000 explorer 5.0 with 66k miles on it for $350. Good deals can be had on these engines...

[mustangrfast88]

i see i might have to go that route and go buy a junkyrd motor but i just really wanted the heads since the explorer motor has hyper pistions and got a forged bottom end and was going to spray a little shot on it

[mustangrfast88]

i think i am going to just spend the money and get edelbrock rpm heads with the 1.90 1.60 valves and take some weight off the nose

[COOP]

I didnt see anyone mention it previously, but the GT40p heads have smaller exhaust valves than the regular GT40's. Regulare GT40's have larger than E7 exhaust valves, where the P heads have the same size exhaust valves as the E7's

[Timido]

I dont think they are that different. Get the one you get the best deal on.

[mustangrfast88]

i see well i am going to have to start looking for something better then stock because i just got a hell of a deal on a cam and if i am that far down on the motor i am going to change the heads out too

[Goober]

I'm running BBK shorties on my P head motor just fine.

[85_SS_302_Coupe]

Anyone know the difference in HP ratings between the last 5.0 Cobra vs. the last 5.0 Explorer? That might give you a hint in how much better the P's are, but also keep in mind that the Explorer uses a different cam and was geared more towards emissions.

[mustangrfast88]

decided i am going to just save some money up and get edelbrock performer rpm 2 heads

[Steves LX]

I just put a set of GT40P heads on my car this past Friday. I have BBK long tube headers and just had to use 90 degree plug wires. The best investment I have made in a while.

[mustangrfast88]

i see well my headers wont work and everplace i am seeing gt40p-s are like 500 -750 that why i am going to get the performer heads

[92BlackStang]

i see well my headers wont work and everplace i am seeing gt40p-s are like 500 -750 that why i am going to get the performer heads

you arent lookin hard enough call junk yards

[mustangrfast88]

i see i will have to look into it

[PaulFiveOh]

Based on all of this:

Are GT40 heads better than GT40P heads in terms of flow and power making?

[12seclx]

I *think* the p heads actually out flow the regular 40's in stock form...
The p head is 58-59cc and the regular 40's are 64-65cc....

[PaulFiveOh]

I don't understand then.

Are you saying the P heads are smaller in Combust. Chamber size but flow better the GT40 heads which have bigger Combust. Chambers?

If that is correct, I can only assume that you are saying P heads are drastically more efficient then 40 heads.

[kennebellcobra]

I don't understand then.

Are you saying the P heads are smaller in Combust. Chamber size but flow better the GT40 heads which have bigger Combust. Chambers?

If that is correct, I can only assume that you are saying P heads are drastically more efficient then 40 heads.

Smaller chambers(area around the valves)up your compression ratio

[12seclx]

Intake Flow @ 28" H20

---- .100" .200" .300" .400" .500"
GT-40P 61 128 169 195 196
GT-40 54 107 157 183 192
E7TE 59 114 144 156 156
GT-40 (Y303) 64 114 167 199 213
GT-40 (X303) 53 114 170 207 226


Exhaust Flow @ 28" H20

---- .100" .200" .300" .400" .500"
GT-40P 52 90 123 135 139
GT-40 47 94 119 128 128
E7TE 42 78 105 115 116
GT-40 (Y303) 52 98 128 137 134
GT-40 (X303) 50 106 139 153 161

OR... go to:

http://www.stangpro.com/html/articles/gt40p_files/gt40p1.htm

[PaulFiveOh]

Ah I understand now

[NXcoupe]

The P's do more exhaust flow with smaller valves, I wonder if anyone has any flow numbers with the larger exhaust valve in it?

[12seclx]

That would be neat to see...
I was surprised that the p-heads actually fair pretty well
considering how much you can pick a set of them up for...

For the longest time, I thought the regular gt40's would
dominate the p's.... but I was wrong...

[PaulFiveOh]

This is an awesome thread btw.