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Discussion Starter · #1 ·
I purchased this car 5 month ago and fixing it and running it, I checked the spark plugs when I first got the car and they were beatup so I put new spark plugs Autolite AR3933 racing same ones The previous owner had put. The gap was around 0.025”, I put the new ones around 0.040”, I just wanted to monitor them while I tune it. i drove the car about 300ish miles and today I took them off to gap them to 0.055” based on online and friends recommendation. See photos below. 7 of them were black on top and one had some oil on it and looked beat up for only 300 miles, now I know I could be running rich and I am working on adjusting that and timing, but does this one spark plug tell me? Anything to worry about? The car has a very aggressive cam and DUI distributor, should I change the spark plugs to another model? Appreciate any help
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Hard to beat Autolite 45s.
If you're running a dual-plane manifold, you likely have a mixture screw on one side backed out too rich.
 

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a. No need to run a wide gap unless you're having misfire issues due to extreme cylinder pressures or mixture degradation (natural EGR effect) or extreme lean mixture.
b. Which cylinder had the "beat up" and "fouled" plug?
 

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Discussion Starter · #4 · (Edited)
a. No need to run a wide gap unless you're having misfire issues due to extreme cylinder pressures or mixture degradation (natural EGR effect) or extreme lean mixture.
b. Which cylinder had the "beat up" and "fouled" plug?
Looking at that one spark plug, I am thinking it might be missfiring! You dont think so?
Cylinder #6 had the fouled plug
 

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Hard to beat Autolite 45s.
He's holding a gasketed plug with 14mm threads - Autolite 45s are a tapered seat 18mm plug.

The second plug looks like it had combustion gasses leaking past the gasket. Make sure you torque them to spec. Huge plug gaps gain you nothing as Woodchuck noted, set them at .040" and forget about it. I'd do a little Googling on how to read plugs.
 
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