[Mister Pontiac]

Originally Posted by Rocky Rotella

• “O” denotes Grand Prix’s 400 4bbl and base 428 4bbl specific 670 assembly.
• “(blank)” denotes 9787603-specific 670 assembly for AUTO trans GTO and Firebird 400s and 428 H.O.
• “Z” denotes 9787608-specific 670 assembly for MANUAL trans GTO and Firebird 400 and 428 H.O.
• “X” denotes the Ram Air-specific 670 assembly for the 400 Ram Air option in GTO and Firebird.

This is simply my best guess at this point. I cannot claim any accuracy just yet!

Thoughts?

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...

[Rocky Rotella]

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...

Thank you for the info!

So the question now remains, was "unstamped" used to denote the GP's 400 and base 428 4bbl cylinder head assembly up to a certain point? And was the "O" assembly that may have been dedicated toward GTO and Firebird 400 automatic applications eventually used on the on the GP's 400 and 428 4bbl, effectively eliminating the need for the "O" stamped casting entirely?

[Mister Pontiac]

Originally Posted by Rocky Rotella

Thank you for the info!

So the question now remains, was "unstamped" used to denote the GP's 400 and base 428 4bbl cylinder head assembly up to a certain point? And was the "O" assembly that may have been dedicated toward GTO and Firebird 400 automatic applications eventually used on the on the GP's 400 and 428 4bbl, effectively eliminating the need for the "O" stamped casting entirely?

Great point, Rocky.

That theory would align with my engine (w/o stampings). It is indeed a late 67 build. F227 on the intake, although I haven't had the valve covers off since I installed it. Can't verify their date(s) at the moment, but I can safely assume they are close.

[Ram4king]

Ever see a set like this?

[GRX]

Originally Posted by Ram4king

Ever see a set like this?

Yes. Have a pair on my shelf. Seems the '061' numbers have two configurations.

>> http://forums.maxperformanceinc.com/...d.php?t=503112

[Rocky Rotella]

Originally Posted by GRX

Yes. Have a pair on my shelf. Seems the '061' numbers have two configurations.

>> http://forums.maxperformanceinc.com/...d.php?t=503112

Thanks for the photos!

That's correct. I've seen them both ways.

[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.