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Old 04-30-2015, 11:43 PM   #1
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Gt40p heads

Hello everyone,

I recently purchased a set of used gt40p heads and am looking to have them redone. What are some good and cost efficient things to have done to the heads the clean them up and allow them to breathe a little better? Also, I am going to put a e303 cam in.. Will I need to go with 1.7 or 1.6 roller rockers? Any brands to stray away from? Plan on just going with the TFS springs.. Any and all information is greatly appreciated!

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Old 05-01-2015, 07:31 AM   #2
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Well to help those heads breathe and work well with that cam I hope you have an aftermarket intake.

Also read this website as there is plenty of good info there.

Also in regards to "cleaning up" the heads....well to port them it will cost you some cash and it is usually not worth it cause it will put you into used aluminum head territory. Now the GT40's are a nice budget upgrade and should give ya a boost in power tho.

Scorpion makes a nice roller rocker as well as the usual suspects. Stay away from Pro Comp rockers seen 2 different sets fail on 2 different cars.
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Old 05-01-2015, 10:18 AM   #3
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Yes, I have a Holley systemax upper and lower.. With all the needed air and fuel bolt ons. I guess my main concern was will I have issues with a e303 cam and 1.7 rr, I get easily confused at the math required haha.

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Old 05-05-2015, 07:00 AM   #4
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The e303 cam has .498" lift with a 1.6 rocker arm.If you add a set of 1.7 rockers to it,lift will go up to .528". The valvesprings you listed are good up to .542-.550" lift if I'm not mistaken.Here is another good link related to gt40-gt40p information.

Anything/Everything GT40P - Ford Mustang Forums : Mustang Forum
91 LX 342ci(10.5:1)
TFS 190cc(stage ll)
TFS track heat
XE276HR .544" .544"
Flowtech 1 3/4"
Prochamber w FM
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Old 05-05-2015, 08:16 AM   #5
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Don't port them, that's a waste of money. By the time you pay to have them fully done and assembled with all new parts you might as well just buy a set of ready to go aluminum heads. Trick with the GT40s is to keep them under $500 fully freshened up including the cost of the heads. After that its just diminishing returns really.

-New seals/locks/retainers/springs
-DIY grind down the EGR bumps

That's really it. E cam is fine with 1.7 rockers, you will have to measure for your pushrods but that's any assembly. That intake will work fine with the GT40s. Motor should make around 275/310 to the wheels. Throw a 125 shot on top of all that for track days.
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Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.
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