Recommended spark plug gap

rockfla

rockfla

Well-known member
What is the recommended spark plug gap for a "stock" flathead, do today's fuels dictate a change from 1935 specs??? Ive seen .016 to .035???
 
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In a original 1936 Reference Book (owner's manual) it says .025 inch, and that works for my 1936.
 
Being that I was a middle child of three, I always go for something in the middle so that everyone is happy. I'm taking a few weeks off from the woodshop to fix things up around the place and tinker with things. Now I know what I'm doing after lunch. I think mine are at .032ish.
 
.032 is too wide for a standard ignition ORIGINAL flathead. .025 is the original factory setting but I have found that .027 or .028 will give a smoother idle with our modern crap fuels, Regards, Kevin.
 
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