Gt40P Heads Spark plug Gap.

jclose11

Member
Jul 23, 2008
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I did a complete tune up on the 1990 mustang and its developed a miss, breaking up when going about 2000 rpm. I double and triple checked my firing order and timing and both are good. My question is has anyone ever gapped a spark plug too much and had problems. I've messed with plug gap before in my s10 with a 350 and never had any issues. Now this car has gt40p heads ,engine is a 302 and I'm running autolite 764 plugs in it which old owner had in it. I gapped them at .054like I have on my other mustangs. Did a google search and search on here people are all over the place with the gap with these heads and plugs. Anyone run a setup like this or have any suggestions , Going to pull out whatever hair I have left. I have a ms2 ecu not sure if that effected the tune .

Did plugs ,wires ,cap and rotor. double checked plugs yesterday and gaps are what I set them at.
 
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stanglx2002

CT Material here
Mod Dude
Jul 7, 2005
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You can keep the plugs at that gaps, but I typically like mine at .05. The issue most likely is in the tune, and there are quite a few of us running them on here. I do recommend posting your .msq and a datalog of the issue happening to assist you further.
 

revhead347

I have face herpes.
15 Year Member
Jun 14, 2004
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Acworth, GA
That gap should be fine. What was included in your tune up? Cap/Rotor, plugs, PCV, normal stuff?

Kurt
 

John Dirks Jr

5 Year Member
Jun 28, 2013
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Re-arrange the routing of the ignition wires to whet extent possible and use loom clips to separate them as much as possible from touching each other. Its also possible to have a bad plug right out of the box. Happened to me recently. Before you chase your tail too much, put the old plugs back in and see what happens.