[ck67goat]

Originally Posted by Mister Pontiac

Rocky,

Just to add in another bit of possible confusion, I have a base YH 428 out of a 67 Grand Prix that appears to me to be blank (no stampings). I double checked again today just to be sure, and I can't find any stampings. The heads do have some rust on them, but after wire brushing the area, I cannot see any remnants of a stamping on either head. So...

To the best of my knowledge, this engine has not been apart since it left the factory 50 years ago. From what I understand (from a fellow PY'er I bought it from), it was pirated from a 67 GP back around 1971 following an accident that destroyed the car. After that, it sat in two different garages for 40 years untouched before I bought it and installed it in my wagon. It still has not been apart.

So if its history is accurate, mine in a base 428 out of an automatic GP, yet it has no stampings (blank).

Hmmm...

I've seen blanks like those almost 30 years ago at a car show. I believe a full size 67. To my recollection, the owner said they were service replacement heads. I could also swear I heard somewhere it was not uncommon for the 670s to be replaced by the dealer, can't remember why or where. Oddly, I have a 67 YK block from the original owner and the 670s were dealer replaced by 62s that were cast in the early 70's, so maybe they either stopped casting or never did cast service replacement 670 heads for some reason. I'm going out on a limb to guess maybe it's because the chamber design was no longer being cast. Would be interesting to know which chamber design your heads have.