V8 spark plug fitment?

Posted by Dave Brownell On 2016/8/13 14:25:22

My newly acquired Executive hardtop is running a bit rougher than the Esquire so I decided it was time for a minor electrical tuneup. The car has not been licensed since 1982, so the Champion H14Y plugs in it are probably at least that old. I went to the Parts X-Ref and shopped all of the in stock plugs with those numbers at my local NAPA store. They had only the NGK and Autolite numbers behind the counter, but showed pictures of both the Bosch and AC on the parts counter monitor. There was no availability of the H14y Champions, either by pictures or by touch. The new plugs appear to have correct threads but the threaded shaft is almost twice as long as the old ones. I am reluctant to even try them for fear that they may extend too far into the combustion chamber and cause interferance. Has anyone used these referenced plugs with the longer threaded shafts? NAPA was willing to special order the H14Y plugs from the distributor, but there's no assurance as to the same threaded shaft length as the old ones I have in the engine. I'd rather stop work until I hear from other V8 owner mechanics.