Skip to main content ↑ ↓
Topic: gt40P heads and stock manifolds (Read 7114 times) previous topic - next topic

gt40P heads and stock manifolds

Has anyone treid the gt40 heads with stock exhaust manifolds?  Just curious....Was thinking of maybe clearing some stuff of my shelves

gt40P heads and stock manifolds

Reply #1 –
Stock exhaust manifolds are ONLY good as recycling material.
'88 Sport--T-5,MGW shifter,Trick Flow R intake,Ed Curtis cam,Trick Flow heads,Scorpion rockers,75mm Accufab t-body,3G,mini starter,Taurus fan,BBK long tube headers,O/R H-Pipe, Flowamaster Super 44's, deep and deeper Cobra R wheels, Mass Air and 24's,8.8 with 3.73's,140 mph speedo,Mach 1 chin spoiler,SN-95 springs,CHE control arms,aluminum drive shaft and a lot more..

gt40P heads and stock manifolds

Reply #2 –
It *may* work but you'll just choke a bunch of power out of the GT40P heads, which would make it a waste of time ;)
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

gt40P heads and stock manifolds

Reply #3 –
I know those heads use a manifold that looks like a cut up and hacked up stock mustang headers. And with the angle of the plugs I don’t know. But like they stated above why waste your time. Money can’t be an issue there’s someone always giving away stock stang headers or for cheap same for the h-pipes,

gt40P heads and stock manifolds

Reply #4 –
There is a reason for everything!  I have headers (for gt4oP)and an x pipe to put on if I wanted to later ...However I have a little bet going on Hooptie vs hooptie.  My xr7 vs 99 crown vic..So I need it to appear stock..For now.  I even have an extrude honed upper and lower which made 314rwhp on my stang....So I think I can do it..I would perfer to besat him by quite a bit..I may try some porting of the manifolds..But I dont know

gt40P heads and stock manifolds

Reply #5 –
It has to be stock?Your car should beat his without the new heads then.If you DO decide to install the heads,and use factory exhaust manifolds,you may need to install new plug boots on the spark plug wires to help clear the manifolds.Are you guys going to be inspecting each other's cars?I don't see what would kill you by installing the headers and X-Pipe.How do you know his is totally stock?Installing the Extrude honed parts and heads is pointless without the exhaust as well.Just leave the car stock until you're ready to do it all the right way.That's a lot of work just to prove you can outrun a Crown Vic.....which in my opinion,doesn't really leave anything to brag about anyway.
'88 Sport--T-5,MGW shifter,Trick Flow R intake,Ed Curtis cam,Trick Flow heads,Scorpion rockers,75mm Accufab t-body,3G,mini starter,Taurus fan,BBK long tube headers,O/R H-Pipe, Flowamaster Super 44's, deep and deeper Cobra R wheels, Mass Air and 24's,8.8 with 3.73's,140 mph speedo,Mach 1 chin spoiler,SN-95 springs,CHE control arms,aluminum drive shaft and a lot more..

gt40P heads and stock manifolds

Reply #6 –
All I really need to do is find out if the factory manifolds will clear.  Restrictive as the wanna be dual exhaust on my car is its staying for now.  If the gt40p dont clear I have a set of gt40's I can use. I can always do the exhaust later if I like.  But for now it will be what it will be

gt40P heads and stock manifolds

Reply #7 –
Use the GT40s. They have the same ports and valve size as the Ps. The only difference is the sparkplug angle.
88 Cougar LS 5.0 .030 over, ported E7s with GT40 valves & trickflow springs, Proform roller rockers, HO cam, removed air silencer, K&N filter, smog pump delete, 2.25" dual flowmasters, Pacestter H-pipe & headers, HO computer, 65mm TB, Explorer intake, 19# injecters, 3.45s, rebuilt posi, and TCI shift kit.

gt40P heads and stock manifolds

Reply #8 –
Bruce I know..I also thought the GT40P had a smaller exhaust valve . Flow numbers are different as well

gt40P heads and stock manifolds

Reply #9 –
Quote from: DamonSlowpokeBaumann;288860
Bruce I know..I also thought the GT40P had a smaller exhaust valve . Flow numbers are different as well


Thats new to me. I worked at a machine shop for seven years and never noticed any difference in the two.
88 Cougar LS 5.0 .030 over, ported E7s with GT40 valves & trickflow springs, Proform roller rockers, HO cam, removed air silencer, K&N filter, smog pump delete, 2.25" dual flowmasters, Pacestter H-pipe & headers, HO computer, 65mm TB, Explorer intake, 19# injecters, 3.45s, rebuilt posi, and TCI shift kit.

gt40P heads and stock manifolds

Reply #10 –
I am trying to get ahold of a gt40 explorer engine instead....But I WISH I KNEW THE ANSWER!!!

gt40P heads and stock manifolds

Reply #11 –
Quote from: DamonSlowpokeBaumann;288860
Bruce I know..I also thought the GT40P had a smaller exhaust valve . Flow numbers are different as well



Iron GT40 1.84 intake valve, 1.54 exhaust valve.

Iron GT40P 1.84 intake valve, 1.46 exhaust valve.

The GT40P has a better flowing chamber so Ford could use the smaller exhaust valve yet still get the same flow out of the head as a Iron GT40 with a 1.54 exhaust valve.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

gt40P heads and stock manifolds

Reply #12 –
That I knew however it seems there is still the debate on whats better...... Me I have no idea

But what I reallly wanted to know......WILL MY CAST IRON MANIFOLDS WORK!!!!:O)

gt40P heads and stock manifolds

Reply #13 –
Head flow chart.
88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, bunch of other stuff.

gt40P heads and stock manifolds

Reply #14 –
Quote from: thunderjet302;289185
Iron GT40 1.84 intake valve, 1.54 exhaust valve.

Iron GT40P 1.84 intake valve, 1.46 exhaust valve.

The GT40P has a better flowing chamber so Ford could use the smaller exhaust valve yet still get the same flow out of the head as a Iron GT40 with a 1.54 exhaust valve.



P's also have a slightly smaller combustion chamber....
-- 05 Mustang GT-Whipplecharged !!
--87 5.0 Trick Flow Heads & Intake - Custom Cam - Many other goodies...3100Lbs...Low12's!