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Looking for the thread specs the spark plug holes in a 66 I-6 (I assume that it's the same for any vintage Ford). How many threads per inch, coarse vs fine and diameter.

Basically if I was trying to find a bolt to fit in the spark plug hole, what are the specs I'd use. I'm not looking for a bolt, but something else, but it's the same info.

Any ideas?

SprintCC
 

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Why not examine a spark plug with a precision ruler? You can count the threads/inch, and the outer diameter and come pretty close to the proper bolt size.

Or, take a spark plug with you to a hardware store, and match up the bolt to the threads of the spark plug. The threads should mate exactly side by side. That's what i have to do, 'cause I have no depth perception and can't tell a #8 screw from a 1/4"!
 

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Plugs should be 18 mm....I can check the thread pitch if you want..... if someone had an 11/16" 16tpi bolt, that might work...

When I make adapters to go into plug holes, I just bust out the porcelain and either weld or thread an adpater on or in...

Let me know if you need more info...
 
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