Quote:
Originally Posted by GOSFAST
Hi Anthony, plug lengths are really considered a "non-issue" here anymore, simply choose the plug you want to use, take the heads to a "decent" machine shop and tell him to "make it happen",
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If you can't find an exact fit, I would at least try to find the longest plugs that I could. Sometimes the installation may need to be modified to fit exactly, but to modify (someone earlier mentioned "chamfer") the heads to use a, say, stock H10 or equivalent would be a mistake in my book, Threads in cast iron are stronger than those in aluminum. The original designers knew this, which is why most after market aluminum heads call for deeper than stock plugs. Most used heads I see have one or several Helicoils in them. I believe this is the result of installing H10's with a breaker bar by over enthusiast amateurs. Back when I raced snowmobiles (with aluminum heads), we always used the wimpy little stock spark plug wrench to avoid stripping the plug threads.