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Discussion Starter #1
I have NGK FR5's in them now (I think). Don't remember what I gapped them at. But I have a feeling they are not what they should be with my MSD box.

I know some of you guys use Autolite 3924's which is what I'll end up using but what about gap with my MSD 6 box? Stock gap is at .054? Should I try .060? Do you go higher or lower with a better ignition system?

Thanks.
 

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Discussion Starter #2
Anybody guys? BUMP.
 

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Discussion Starter #4
That website says those plugs are for cast-iron heads. I have the GT40x aluminum heads.

Anyhow, I went ahead and regapped my existing FR5 plugs to ~.058. Runs much better and pulls a little harder. Broke my Nittos looses rolling from 2 grand in 2nd gear! Plugs were looking white all around with a spot of carbon. No pigging though :confused:.
 

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The crate motors with
those heads come with AGSF-32C.
it says gt40/gt40p.
the gt 40p are the cast iron heads
 

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Discussion Starter #6
There is also GT40 cast iron heads. They came on the 93-95 Cobra's.

GT40x and y aluminum heads
GT40 cast iron 93-95 Cobra's
GT40p cast iron heads from 97 up Explorer's
 

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i think the only difference in the gt40/gt40x ALUMINUM CYLINDER heads are XTRA PERFORMANCE "TURBO SWIRL" as far as the plugs go they use the same. the gt40p has a different plug angle.
 
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