451Mopar
Well-Known Member
Bird 426 had the answer. The spark plug threads closest to the chamber will have two or three threads discolored compared to the rest of the plug threads.
The -11 is factory pre gaped 0.044".
I also use nickel anti seize on the plug threads. I think NGK says their plugs don't need it? The Champion plugs sure do! I test fit a Champion in a new set of heads dry, just finger tight, and the lower two threads seized. Lesson learned there.
The MSD ignition should not have a problem with the larger plug gap if you are not running boost AND the coil, wires, cap and rotor are up to the task.
Newer cars with coil on plug can easy run the larger gap, no issues with rotor cap phasing and stray crossfires to worry about, and no plug wires that might have marginal insulation.
Just saying you have to look at the whole ignition as a system working together.
The larger the gap (and cylinder pressure) the higher the secondary voltage needs to build up to jump the gap, but that higher voltage might find other places to jump the gap if given the chance.
On these older cars I'm not looking for that last 1 HP so I usually just use 0.035" to 0.040" plug gap.
That might also be a consideration when running the Holley Sniper to reduce RF noise.
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