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Old 11-07-2019, 12:43 PM   #69
GOSFAST
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Join Date: May 2010
Location: Long Island, NY
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Default Re: Spark Plug Protrusion into Head?

Quote:
Originally Posted by AnthonyG View Post
I see a Champion spark plug that has a 14mm thread 5/8” reach on Summit Racing site. Posted as Racing Spark plug but looks midrange for Heat, thoughts? https://www.summitracing.com/parts/cpn-1001/
Hi Anthony, set them up now so you won't need any "special" plugs, it may all come back to bite you at a later time?

The most probable way we would end up "fixing" these Offy's we have here on the shelf would be by welding up the existing plug registers and simply machine them to the correct heights for the .750" plugs, due in part to the head material (aluminum) I would NOT use any "short" reach plugs in these casting as long as I have the ability to make them right!

We would only have to weld on the tops where the plug gasket sits, leaving the existing threads at the bottoms of the holes. Flip the heads, back-drill thru those existing threads and tap a new hole AND new threads through the welded section!


P.S. In the event this entire procedure didn't work 100% we would still have the option at this point to install 8 new threaded inserts. The photo below here shows the type of inserts we would use! If these were for my own unit here I would do the inserts without a doubt! Weld, drill, and tap only would keep the costs in line, the inserts, obviously better, would raise the cost some!
Attached Images
File Type: jpg Flathead Offy Spark Plug Inserts-.750.jpg (68.4 KB, 79 views)

Last edited by GOSFAST; 11-07-2019 at 05:56 PM. Reason: C
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