67 318 spark plugs

[cherokeechief79]

new car to me.........what i pulled out is autolite 66.
autozone looked it up and says autolite 68.
the thread depth is way different.

 

[Professor Fate]

I'll assume you're talking about an LA 318, not a Poly 318 (Canadian cars still used Polys in '67).
Autolite's website says 66.
They do also list 86s, but those are for Poly 318s and don't have enough reach for an LA head.
Search Results | Autolite

 

[cherokeechief79]

thank you....so the ones i took out seem correct.
i once got plugs for a chevy 350 and they didnt have the ones i wanted but they gave me the alternative.
the problem is they were much shorter threads and reach.
they worked fine till the next change but the last threads in the head were exposed and got carbon all over them.
the new longer plugs going in get tight at the last couple of threads and are hard to get to the bottom.