Someone was recently telling me that Bosch plugs have a slightly
different thread form (round vs sharp?) that can cause plug blowouts.
His experience is the other way around, running non-Bosch plugs
in German engines. Just something to keep in mind ...
I'm very very happy with NGK plugs, run them in everything I can.
My street 4A uses BP6EH (except the one hole that's got really
bad oil fouling, where I run BP5EH, a little hotter). You might
want BP7EH for your higher compression. May be tough to find,
but worth looking. Try a marine supplier - those long nose NGK
plugs seem to be popular for some sort of marine engine.
Champions have a bad habit of failing even when new out of the box,
at least for me.
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