GT40 v.s GT40P

NKau · Mar 20, 2004

Was curious if there was any difference in performance between afforementioned heads. Also, were the GT40's found only on '93-'95 Cobras, or were there other sources for them? I'm thinking about trying to pick up a set of cheap GT40's; mainly because I don't want the hassle of changing headers. Thanks for any info.

Timmey9 · Mar 20, 2004

I believe the FT-40s were on explores too until mid 97 when they switched over. The P's havea relocated sparkplug that is deeper into the combustion chamber, this also makes a smaller combustion chamber so you have a higher compression ratio and possibly more power.
I have been looking for a set of P's because i feel they are better than the non p's, but others may disagree.

I read about porting the p's and itis hard to get any more flow out of them without bigger valves. Hope that helps some

mustangdaren · Mar 20, 2004

I doubt the difference would be worth the hassle of using special headers. Take my advise. Save your money and get aluminum heads so you only have to do it once. I have GT40 irons and regret not getting some TFS or AFR heads. You would see an easy 40+ more horsepower with the aluminum heads.

Michael Yount · Mar 20, 2004

The flow numbers on the P's are slightly better than the GT40's. The re-angled spark plugs however won't clear most aftermarket headers, so P-specific headers are usually needed. The P's came on mid-year 97 and later Explorers and Mountaineers. The GT40's came on the Cobras, and the 95 thru mid-year 97 Explorers and Mountaineers. If you have to put emissions equipment on the P heads aren't equipped for air injection or internal egr.

stock50LX · Mar 20, 2004

I agree with the above info. However, you can get more flow out of them, easily but only up to point. Improving flow on the exhaust side is easy. Both heads should work fine for what you want.

Mean88 · Mar 20, 2004

My vote goes for the p's. I personally have them, and I love them. I bought them with stage 1 bowl work and 5 angle valves. This winter I pulled them, and fully ported the heads myself. For my first porting job the car picked up some real power. As far as the headers go, stock ones will work for cheap, and many aftermarket ones will too if you have 90 degree plug boots. I am running mac long tubes with my 90 degree msd wires, and it works great. Changing plugs is easy if you have a 5/8 spark plug socket and an 11/16 wrench to fit over the end of the socket. Good luck with the head choice. If it helps any, my speed density 88GT ran 105.06 in the quarter last summer without the porting I did this winter- not to mention it was on drag radials with shorty headers too.
Ted

NKau · Mar 20, 2004

Well, I had kind of come to the conclusion that I didn't want to mess with the "P" heads because I already have nice headers, and just didn't want the hassle. Plus, people seem to want an arm and a leg for them for some reason. I ran across a few deals on regular GT40's and just wanted to know if they were worth the trouble.

mustangdaren, I have your same thought on the GT40's v.s. aluminum heads. The problem is that I can't find decent deals on used aluminum heads. Decent deals pop up on the edelbrock performers from time to time, but I feel like I'll be kicking myself later for not holding out for some afr 165's.

For all of you watching this post, I am dead set on running an edelbrock performer intake, 65mm TB, and 70mm MAF that I have just purchased as I want my combo to be a complete animal from idle to 6,000 rpm. How much will a set of worked GT40's give up to a set of small valve (1.90/1.60) aluminum heads like afr 165's or performers? Will I have just as much money sunk into the heavier GT40's when all is said and done?

astronut1885 · Mar 20, 2004

I got a new pair of GT40Ps for 400.00 with 1.54" exhaust valves for better flow, and put them on the car. They're a great type of head, and I got my headers for 100.00 in mint condition. As far as them not being setup for EGR, I think mine had all of the provisions, but I'm not sure, as I wasn't there when they were installed and we blocked off all the EGR crap anyway. Bottom line: get a nice set of Ps for cheap and you won't be dissapointed.

thumper460 · Mar 20, 2004

From what I have seen you can use the shorter spark plug and 90* boots and the plugs clear all headers on the Ps. The Ps will put down more power than the 40's but how much bepends on the port work!! apples to apples... the increase isnt worth all the head aches there seems to be on the two heads!! Both rock stock, and Both will kick ass when ported !! To me run the best price, the port work is the same cost on either head... or your own port work. be carefull on HOGGING out TOO much .. and they are good !! I ported a set of GT40s on a 12.70 turbo car, and he droped into the 11.80s!! just with the heads and port work.... so the power is there!! cool??

just me...........................

Thumper

GT40 v.s GT40P

NKau

Timmey9

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mustangdaren

Michael Yount

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stock50LX

Curmudgeon

Mean88

NKau

astronut1885

thumper460

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