Gt40 spark plug gap?
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Mountain Pass
Joined: Jan 2018
Posts: 226
Likes: 11
From: Branson West, MO
Gt40 spark plug gap?
Im working on my 1995 351w 5.8 efi with GT40 3 bar heads, 1.7 scorpion roller rockers and BBK shorty headers and stock intake and stock cam. I just got new spark plugs, 44,000volt coil, new cap and 9mm wires. CJ pony said these spark plugs would fit my gt40 heads. They came pre-gapped at .043. What should I gap them at?
Lead Driver
Joined: Jun 2021
Posts: 5,221
Likes: 805
if copper, .46
Lead Driver
Joined: Jun 2021
Posts: 5,221
Likes: 805
because of copper and nickel, id use .46 too
The reason for .43 on my recommendation if platinum is platinum can hold heat worse, potentially causing predet, but ive only heard of that in boost scenarios
Copper has better heat transfer, nickel is presumably to prevent gap erosion, and iridium plugs use a tiny wire (which is different from the thick center platinums which is why they can handle more heat)
The reason for .43 on my recommendation if platinum is platinum can hold heat worse, potentially causing predet, but ive only heard of that in boost scenarios
Copper has better heat transfer, nickel is presumably to prevent gap erosion, and iridium plugs use a tiny wire (which is different from the thick center platinums which is why they can handle more heat)
Hotshot
Joined: Jul 2020
Posts: 10,471
Likes: 2,633
From: Near Salt Lake City
Bosch plugs in a FORD?
The gap goes with the ignition system
Back when GT40 heads were new, and being used from the factory in the AC Cobra and Shelbys, the gap was .032
With any electronic ignition with some BIG volts, you want to increase that plug gap to around 40-45 thou
The gap goes with the ignition system
Back when GT40 heads were new, and being used from the factory in the AC Cobra and Shelbys, the gap was .032
With any electronic ignition with some BIG volts, you want to increase that plug gap to around 40-45 thou
Thread Starter
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Mountain Pass
Joined: Jan 2018
Posts: 226
Likes: 11
From: Branson West, MO
The spark plugs I ordered, two of the eight are different. Came in an older looking box and the part number is different by a plus sign. So I guess I’m on the hunt for a whole new set…
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Lead Driver
Joined: Jun 2021
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id personally use something like iridium or stay with copper, but i do not like my experience with bosch plugs on these trucks
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