GT-40 heads on Speed Density 5.0 F150 - Hot Rod Forum : Hotrodders Bulletin Board
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Old 02-18-2013, 07:24 PM
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GT-40 heads on Speed Density 5.0 F150

I know the subject has come up alot and ive done a search and not really found the answer i was looking for.

First off, truck is an 87 F-150 5.0L with a speed density EFI, will the GT40 heads make a difference in performance?

And second, can i use the stock F150 intake with the GT40 heads? The other intakes would probably require alot of work and or money to get them to work with the F150.

I am working on my truck. The engine is out and on a stand. Its really nasty and needs cleaned up and the crank turned and new clevite bearings. Its also going to get a comp cams 31-255-5 cam and lifter kit, as well as a melling performance oil pump, cloyes heavy duty double roller timing set, mr gasket engine gasket set, new rings, a set of headers and maybe the GT40 heads. Will any of this mess up the computer since its speed density? The cam is supposed to work with the stock computer, so it SHOULD be ok, but the heads and headers might change the flow through the engine and I dont know if the computer can handle that or not.

Also, what would be involved in changing this truck over to a MAF system? Would it be of any benefit to me with the changes I am planning to make?

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Old 02-18-2013, 08:06 PM
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Not to hijack---but I am also working on a late Ford engine.
Someone mentioned to me to acquire a set of GT40 heads.
I have no clue as to what he is talking about----or what they came on.
Can y'all give me some insight??
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Old 02-18-2013, 08:30 PM
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I'm no expert on the subject, but GT40 heads are supposed to be the best of the stock 302 heads, similar to the way vortecs are for the the small block chevies. GT40P's are considered by some to be even better as they are revised with a smaller and "cleaner" combustion chamber and cleaned up exhaust port as well as a different spark plug location. However, both flow about the same. The P heads have problems with the "improved" spark plug angle causing clearance issues with a lot of headers. Here is a site that tells all about them, including what vehicles they come on. http://www.fiveohinfo.com/performance/gt40-gt40p.html

Due to the header issue, I plan to use the GT40's instead of the GT40P's.


One thing I dont know about (hence the purpose of this thread) is if the intakes will interchange or not. There has been alot of talk about using the intakes that come with the GT40 heads - I dont know if this is because they are better or if its because the GT40s take a different intake. Also I dont know if the Speed Density EFI will be able to function properly with the increased flow of the GT40 heads. It is not as adaptive to changes in airflow as a mass air flow system is.
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Old 02-19-2013, 04:46 AM
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Thanks!!
That put some insight into it.
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Old 02-19-2013, 10:05 AM
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I have been down this road with the stock Ford heads and yes I can get a set of GT40 heads but by the time I have them re-done and ready to go with new valves,springs,retainers, seals and all that and the machine shop bill for a few more bucks I can get a set of World performance or Ford SVO heads and have a real performance head..As fas as the EFI is concerned figure on spending a bit to either hot chip it or modding it so you can get the engine tuned correctly..I do not do EFI myself so I would have to send out for that piece..

In any case if I were to another build on a SBF i woudl plan on aftermarket heads..

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Old 02-19-2013, 05:25 PM
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if your looking to change a lot of things over, I wouldn't waist my time with the gt-40 heads, those who have them want a mint for them and there not worth it. now on the late model explorers with 5.0 in it they have gt-40p heads and a cobra style intake(lower) and are mass air systems, so instead of spending a small fortune on aftermarket stuff find a donor.

but to answer your question. the gt-40 heads are not much different than 5.0 mustang heads, just the chamber shape, they still have thermactor bump in the exhaust, if you find a used set you'll pay around $500.00 then to have them rebuilt about another $250-300.
so unless your racing or need a lot of flow the stock style gt-40p heads off a explorer will due just great.
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