[Rocky Rotella]

Alright guys, I have been trying to figure this out for a while and am hoping you might be able to assist.

There's no question that Pontiac used 670 cylinder heads on its 400 and 428 in 1967, and those intended for the 400 Ram Air were equipped with special valves and springs. Nunzi tells me that he recalls Ram Air-spec 670s being identified by a small "X" stamped into the dime-sized disc over the center exhaust ports.

I've been looking at 670s for a few years, photographing them as needed. I have never found an "X" but I also haven't been able to document an original '67 Ram Air GTO that unquestionably retains its original cylinder heads to verify it.

When speaking of 670s in general, I have found most are blank or so rusty that any stamping is undetectable. My search reveals a recurring trend, however, and that's a small "Z" stamped into some. Has anyone else ever come across this on their 670s?

Looking at vintage parts manual, Pontiac shows two part numbers for the 670 cylinder head. The 9788067 is found on all 1967 400s (except second-type Ram Air, obviously) and 428 HO. The 9788066 is limited to the basic 428 4bbl. Undoubtedly there are different components used to comprise the different part numbers (such as valve springs) that require separate part numbers to differentiate cylinders heads produced using the same basic 670 castings. This may be of significance and directly related to the stamping, but I don't have a 67-dated parts catalog to determine.

So has anyone else found 670s stamped with any characters and/or know of its significance?