WHAT IS THE DIFFERENCE BETWEEN GT40 HEADS VS GT40P HEADS?
The GT40 & GT40P heads had a few differences that are note-worthy, the most importantly being the bump in compression. The GT40P heads had a small combustion chamber ranging from 58-61cc while the GT40 heads had a 63-66cc combustion chamber. The GT40 heads have thermactor holes built in to connect to the EGR/smog equipment whereas the GT40P heads us an external EGR connective system. The GT40P heads also had a different spark plug placement making header choice important. GT40P specific headers are needed unless you use spark plug wires with 90 degree boots to clear the heads.
GT40 & GT40P HEAD SPECS
Head Type Intake Port Combustion Chamber Intake Valve Exhaust Valve
E7 124cc 61cc 1.78 1.46
GT40P 145cc 59cc 1.85 1.46
GT40-Explorer 145cc 65cc 1.85 1.54
GT40 - Cobra 145cc 61cc 1.85 1.54
427 CID 225cc AFR heads, 12.9:1 CR, 230@.050 .740 Lift.
331 CID, 185cc AFR heads, 10.6:1 CR, 224 @ .050
I have made 575Hp Clevelands using Trickflow 195cc heads.
I've seen others make 620Hp with TFS 225 heads, which seems a bit disappointing but probably realistic.
I've made 700Hp at 6400rpm using Yates C3 heads and the D4 heads are even better.
800Hp will take over 7000rpm.
As we all know used Ford Cleveland blocks are getting harder to find and making over 600Hp is just asking to crack a cylinder or two.
Cleveland Block Numbers
1970 2-Bolt D0AE-A,D0AE-C,D0AE-E,D0AE-G,D0AE-J,D0AE-L D0AZ-D
1971 2-Bolt D0AE-A,D0AE-C,D0AE-E,D0AE-G,D0AE-J,D0AE-L D0AZ-D
1971 2-Bolt (CJ) D2AE-CA D1ZZ-A
1971 4-Bolt (HO) D0AE-B,D0AE-D,D0AE-F,D0AE-H ????
1971 4-Bolt (CJ) D2AE-CA D3ZZ-A
1971 4-Bolt (Boss) D1ZE-A,D1ZE-B D1ZZ-D
1972 2-Bolt D2AE-DA DOAZ-D
1972 2-Bolt (CJ) D2AE-CA D1ZZ-A
1972 4-Bolt (HO) D2AE-EA D1ZZ-D
1972 4-Bolt (CJ) D2AE-CA D3ZZ-A
1973 2-Bolt D2AE-DA DOAZ-D
1973 2-Bolt (CJ) D2AE-CA D1ZZ-A
1974 4-Bolt (CJ) D2AE-CA D3ZZ-A
1974 2-Bolt D2AE-DA DOAZ-D
1974 2-Bolt (CJ) D2AE-CA D1ZZ-A
1974 4-Bolt (CJ) D2AE-CA D3ZZ-A
Damper Length Ford dampers come in three lengths—the distance measured from the front face of the damper to the back of the hub.
They are approximately 3”, .35" (~3-3/8") or 4”.
Ford pulleys come in two bolt styles - either 3-bolt or 4-bolt fronts.
3-bolt pulleys are found on dampers with a length of 3"
4-bolt pulleys are used on 4" dampers, and 3.35" (~3-3/8") dampers use both 3 and 4 bolt fronts
This is my Ford information page.
You will notice my website is different from every other engine builders site like Proformance Unlimited ATK Blueprint Engine Factory etc, that is because I don't sell engines, I build them.
In other words, I don't try to talk you into buying anything.
You tell me what you are thinking about building and I'll help you get it.
The builders above have combinations ready to go, I can't build motors as quickly as they can.
I can build them for less and I do build more powerful engines.
Most guys who buy motors from me want some more special.
Write to me and tell me what you are looking for
That said the cheapest 347 or 408 Windsor turnkey engine I build is $7200.
You can get one from another shop for $6900, so if you are shopping price I'm sure you will find it.
I focus on building more powerful combinations.
I build more Ford engines than Chevrolet engines
Write and I'll reply.
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To make 700Hp the easy way use a big block typically 552CID