I have had good experience w/NGK plugs. Their threads are machined so that
they seat squarely into the head when installing, under and angled up behind
the exhaust manifold as they are. They seem to be durable enough, though any
motor with a worn timing chain / nylon cam gear will foul an otherwise good
plug. The previous few thousand of miles before my nylon cam gear failure, I
would have a fouled plug just days after replacing them. After the new chain
/ steel gearset, and a thousand miles, plugs still fire ok. Thus, your
actual MPP may vary.
Eric
'63 Crown Four-Door
'72 Newport Custom Sedan
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