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Old 07-16-2020, 10:06 AM
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Default spark plug gap

MR41T's in a Cigarette with 502's, blowers making about 5 lbs of boost, approx 600 HP...

These are the plugs in the boat, getting ready to replace, curious what I should set the gap at. Thx.




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Old 07-16-2020, 10:08 AM
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.035”
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Old 07-16-2020, 10:18 AM
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.03551.....
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Old 07-16-2020, 02:46 PM
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Old 07-17-2020, 01:16 AM
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Old 07-22-2020, 07:38 AM
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What type of ignition do you have? My old MSD and my new Daytona Sensors called for a larger gap due to the added spark power they provided. If your running stock then .035" otherwise go with the ignition manufacturers suggestion. Other than that you are running really rich.
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Old 07-22-2020, 12:15 PM
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D.U.I ignitions recommend 0.055 which doesn’t work well at all.
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Old 07-23-2020, 10:40 AM
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Originally Posted by ThisIsLivin View Post
What type of ignition do you have? My old MSD and my new Daytona Sensors called for a larger gap due to the added spark power they provided. If your running stock then .035" otherwise go with the ignition manufacturers suggestion. Other than that you are running really rich.
MSD... distributors and 6AL boxes...
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Old 07-23-2020, 11:06 AM
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In that case max .040”

The strength of msd box is being able to fire an otherwise fouled plug. Keeps larger cammed lower quality idle mixture engines idling well. Larger gaps don’t do much but eat ignition parts (caps, rotors wires) in small block and big block chevy engines.
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Old 07-23-2020, 11:38 AM
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Which coil are you running? Some of the newer coils put out a lot more current than the old Blaster. In big bore engines spark strength can make a measurable difference.
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