Community Q&A Question: Low on power after upgrade

Asking About: Mustang Ford Racing GT40x Cylinder Head 64cc (79-95) 5.0L/5.8L


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Low on power after upgrade

I bought the GT40x heads a few years ago for my 89 gt auto from LR. I paired them up with the 1.6 roller rockers and the cobra intake manifold. The car seems to be down on power. I know I've installed it all correctly. Any ideas? Motor only had 60000 original miles and was immaculate internally.
from Elmhurst |
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Accepted Answer
I always think of flow in 3 areas, intake or induction, engine and exhaust. If you change on you will generally have to do something to address all three areas. On the intake side, did you get the egr spacer and throttle body for the cobra upper/lower also? I would run a fresh air kit on something like what you are working on as well. A lot of the flow potential you are after will be held back by the stock exhaust. The computer needs to be dialed in also after you make changes.
from Jefferson |
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on should say one up there. If you push it up significantly you will need to consider a lower gear and a higher stall converter but you should be ok if you stay with a mild cam. - Johnny last year

I did upgrade to ford racing shorty headers and flowmaster am thunder exhaust, but left the stock cat pipe on. I assume maybe bumpimg up the timimg to say- 14 degrees advanced and purchasing a hi flow x pipe w/o converters could free up power? Cam is the stock unit. Maybe switching to a slightly bigger cam as well? Any suggestions that might work with that setup? - Jack last year

What is it set on now timing wise? I would try 12 and 14 and see which it likes better. Also, it is not just the initial timing but also the curve may need to be adjusted as well. The computer should adapt ok to basic bolt ons but I would be wondering what the a/fr looks like with the changes you've made. I run an AEM analog a/fr(wideband) gauge to help with tuning but I run a Q650 carb on my car. - Johnny last year

A better cam will always help when you upgrade the heads but you don't necessarily need that to get some noticable improvement in power. - Johnny last year

A better cam will always help when you upgrade the heads but you don't necessarily need that to get some noticable improvement in power. - Johnny last year

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- Johnny last year

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- Johnny last year
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Did you change out camshafts as well when you swapped the heads? First thing that comes to mind is to make sure the timing is set correctly. Having your timing retarded to much will definately effect the power output. as far as the heads themselves go they flow better than the e7TE heads but you are really leaving alot of potential on the table if you are still running a stock cam. The GT40X heads have a 64cc combustion chamber which is slightly larger than the Stock E7 head. Depending on the thickness of head gasket you are running, that could have dropped your compression ratio a little from what the OEM motor was.
from hewitt |
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