GT-40 heads

[Drake_tr7]

As most of you know I bought a "345hp GT-40" crare motor from JEGS...well it was billed as 78-93 replacement yeagh right???....
GT-40 head WILL NOT WORK WITH SPEEDDENISITY !!!! Foed will not tell you that....

[Drake_tr7]

450 hp...

[pro-five-oh]

Plenty of speed density Mustangs run crazy motor combinations, don't sweat it, it will work. If you keep the stock fuel injectors (I forgot which parts you have) you shouldn't have a problem with any aftermarket head.

If it doesn't run right after installation , tow it to the nearest Mustang speed shop with a Dyno and chip burning software. They will tune it to the parameters of a GT-40 crate engine. It'll work. Or get a laptop and a www.twEECer.com (http://www.twEECer.com) and tune it yourself.

[ September 11, 2005: Message edited by: pro-five-oh ]

[Drake_tr7]

I just did it MAF conversion sensore calibrated to 30lb injectors and a bigger fuel pump I bought it all....

[Drake_tr7]

Pro_five the GT=40X heads are different thicker decks for one

[Drake_tr7]

and the gaskets are different

[pro-five-oh]

That doesn't affect the operation of Speed Density EFI. You can tune SD to work with just about any engine combination.

EDIT: and if you are using stock 19lb-hr injectors the computer will probably run just as well on GT-40 heads as it will with stock heads. Ask 90LSC, he has stock speed density with Trickflow heads, a design even more radical than Gt40s.

[ September 11, 2005: Message edited by: pro-five-oh ]

[Bluegrass]

The GT 40-345 offering has either an B303 on an E303 cam.
These cams do not work well with speed density.
It's not the heads.

[Drake_tr7]

From ford engineers to mass air conversions and a few I talked to at Ford said " speed density will not run w/those heads"

[Drake_tr7]

Well Ken I'm going to run the 303 doing the MAF conversion,30 lb injectors w/the approiate fuel pump...is the regulator a problem? Blower next year run it in for now

[Bluegrass]

Well what can we say? The heads have little to do with speed density but everything to do with camshaft timing on SD.
Since you are going Mass Air, it's a moot point now..
You go with whomever you want to accept advice from.
Those same people will likly tell you you can't supercharge an SD engine but we know it ain't so don't we?

[Drake_tr7]

Know all ye...if you buy a motor from JEGS ask questions...They don't know...get your answers before you spend your money...
I'll get the big HP but I'm spending about 2 grand more than I had planned FORD motorsports will not tell you zip a motor in a crate is all you get...no note no nothing
Just a motor in a crate
And no you can't run speed density w/those heads well maybe w/a tweeker..
I bailed and bought it all..P on it MAF here we go

[Drake_tr7]

Blue I bow down if that gasket hadn't blown I'd still be an ass. Now I get to feel what a blown markVII feels like

[Drake_tr7]

break in the GT-40 then she gets a blower

[gadget73]

Sometime this summer I'll be helping someone do a GT40 Explorer engine swap into a Towncar, most likely keeping it speed density and controlling the whole mess with a Mark 7 ECM. Should work out OK, tho it might be marginally more powerful or efficient if we go mass air. We'll see what we end up doing with it, but it won't be all that hard to convert it. MAF and a stock Mustang ECM will run the cost up maybe $150 plus the wiring harness to convert it. Not a big deal. The more involved part will be changing the cruise control system to the older non-integrated setup if we go mass-air. We're also planning to do Explorer accessories on the front of the engine, and somehow try and integrate the variable power steering assist with the cruise control operation. That I expect to be much harder than getting the engine running properly on an ECM that was never meant for it.

And FWIW, I agree that head changes have very little to do with messing up an SD system. They're a bit more tolerant than people give them credit for, but cam swaps they just do not appreciate very much. They also don't much care for different injectors than intended or vacuum leaks.

[skarhed]

Speed Density can work with any head and any cam, blown or naturally asperated. Some of the aftermarket EFI systems used on the mondo horsepower professional racers are speed density. But it(the SD computer ) won't work in a stock configuration with changes that affect that air flow. Even a Mass Air system must be calibrated for a particular engine configuration. They both do the same thing, measure how much air the engine is getting and telling the fuel system how much to add to that air, they just do it a different way. Think of a huge spreadsheet of solutions for a multi-variable equation, if this, that , this and that equal these then fuel equals this. When you change the cam, flow characteristics of the heads and other things then the solution to that equation is not in the look-up tables stored in the ECM memory. When you use a TweeCer or other reprograming system what you are doing is giving it new values for the look-up tables that will work with the changes in the inputs. You can drive yourself nuts hanging parts and guessing or following hearsay, or you can deal with a knowegeable tuner who will put the car on a chassis dyno and tune it based on real time measurements. Cheaper in the long run.