Gt-40 Gt-40x Gt-40p Whats The Difference

[big_rob]

What is the performance and spec difference between the GT-40, GT-40X, AND GT-40P?
AND...
should i wast my time on GT-40 heads or spend the extra dough on tfs twisted wedge heads

[stevehaygood]

Twisted wedge heads is the way to go if you got bucks... There are a couple of GT-40 heads out there. The regular cast iron heads come off a 302 and can be made to fit a 351W if you drill out the headbolts to from exisitng 7/16 to 1/2 inch. Hot Rod Magazine had an article bout 5-6 months ago. I think the other numbers mean cast iron or aluminum I have been told the "P" series is the best and any 302 or any small/large blocks from Mexice are good becasue there is extra nickle content in their
ores down there
Good Luck

Steve

[auto10x]

The GT-40X heads are the ones Ford uses on their crate stroker 392 engine.
auto10x
Bill

[zipzip]

Try this website to explain the diff's: http://www.themustang-net.com/tech_articles/gt40p.shtml

I used the GT-40P on my 302 mainly because the $$ were about double for the aluminum....

[SFfiredog]

The Ford Motorsport GT-40 head (not to be confused with the original GT-40 heads used on the LeMans GT-40s of the '60s)
is iron and offered over the counter and was later used on the '93 and up Mustang Cobras and '93 to -95 Lightning pick-ups.
The GT-40 P was original issue on 5.0 Explorers and while the same specs as the earlier GT-40 head, the spark plugs were relocated in the combustion chamber for better performance and emissions. THe GT-40 P head requires different exhaust headers than the earlier GT-40 because of the relocated spark plug.
The GT-40 X head is aluminum and has slightly larger valves the the iron GT-40 heads and is the standard aluminum head for Ford'scrate motors.
All GT-40 heads offer excellent low valve lift flow characteristics and are very good for a mild to somewhat hot street motor and offer good value for the money.
--Mike

[big_rob]

thanks mike. i have a stock 302 out of a 91 gt (look at my pics) im currently swapping the efi to carb (holley 750 with vac 2nd and edel performer intake) and im waiting on a 347 stroker kit.
Are the stock heads fine for now?
or should i go with something better like the gt40p's
and finally are gt-40p's going to do the job or is it worth the extra $$$ for aluminum tfs or gt40x heads? or any other make that you might recommend!?!?!
i got a little extra to spend on the engine but would still like to keep costs down for now.
my biggest concern is im spending all my money in the engine and it will take longer than expected to finish the kit.

[SFfiredog]

I looked at your photos and was very distracted by one certain one
So much so, I forgot your question!
Seriously, I have a friend with a FFR with a stone stock EFI 5.0 H.O. and it is remarkably fast just the way it is.
I would suggest if the donor motor is in good shape I would just install the manifold and carb and finish the car.
You will need a distributor that is compatable with the roller cam in your engine. MSD makes one that will work or you can use a '85 5.0 H.O. distributor. This the only year the 5.0 had a roller cam and a carb.
Finish the car. It will always cost more to finish than you expect. Always. There is no such thing as extra money when building
a kit Cobra!
Once the car is finished, put some miles on it and get used to it. Later, pick up another core short block (they are dirt cheap and easy to find) and build a hotter engine like a 347 with
AFR or Edelbrock heads and a hotter cam.
HTH,
--Mike

[Wayne Maybury]

You may want to consider matching the cam to the carb since not all EFI cams work correctly with a carb. I am not saying that you have to change the cam but I am saying that you should talk to someone that has experience in this area.

I couldn't see a Mustang in that picture. Now those are looooonnnnnnggggg legs.

Wayne