[Rocky Rotella]

One point to add.

What further fuels my suspicion about the "(blank)" 670 being specific to auto applications is that I have been involved with two 1967 Pontiacs (a GTO and a Firebird) in the recent past. Both automatics with original cylinder heads, and neither had any visible stamping.

[Aluminum Chief]

Just put a ladder up to my Ram Air 67 GTO and got the money shot.

Unrestored 67 Ram Air 4 Speed California Car.
YR Engine Code.
EUN on engine matches the build sheet. Both heads have the X.
I think the spark plugs might need changing, they might be originals too.

KC

[Rocky Rotella]

Thank you, Ken!!!

[GRX]

Great topic. Love this kind of stuff.
Makes perfect sense they would stamp heads for the reasons you described.

My 670 heads have no stamps. Have not had the valve covers off in a while but do seem to remember they are January '67 castings. Do know the block they came on is an October '66 cast date with 'WT' stamp that comes up as 335-hp manual. Which was confirmed by presence of clutch pivot stud. Bought the engine in 1986 so no telling what had been changed before that time. Not much help I know.

[Aluminum Chief]

Sure Rocky, I`m glad to help.

And I agree with Steve25 about Pete Mc Carthy, I can`t even count the times I opened up his book for info. Hope he`s doing well. I won`t give a shout out to him only because I hate that saying but I will take my hat off to Pete.

[Ducks Goat]

Originally Posted by steve25

Ducks goat and 77 Poncho , I see the remnant of a O in atleast one each of your heads.

In person the one of mine that appears to be a O is raised not stamped, but I am kinda blind.

[johnta1]

Thanks for the pics KC!

I think the spark plugs might need changing, they might be originals too

The plug is Autolite, so not original.

[Ducks Goat]

Hate to throw this ringer in there but my '67 GTO is a manual trans and the '67 Firebird is an auto trans. Both of these are 100% original engines.

[242177P]

Originally Posted by Rocky Rotella

• “O” denotes Grand Prix’s 400 4bbl and base 428 4bbl specific 670 assembly.

Umm, no.

The heads I posted are both automatic GTOs.
Trend I spoke of was O for auto, Z for stick.
Stamped heads also have earlier dates. HTH

[steve25]

All of this new info may end up having a deep impact on the 67 show car owners!

[vidguy]

My M146
670's that are original to my 67 Fremont built YS Auto GTO with no AC have "O" stamps on both. Pics shows block date , head date and stamp. I can take better pics if needed. but they suffice here I think.

[Rocky Rotella]

Originally Posted by 242177P

Umm, no.

The heads I posted are both automatic GTOs.
Trend I spoke of was O for auto, Z for stick.
Stamped heads also have earlier dates. HTH

I think we may be on to something!

[steve25]

Yes, as now we know that there where good reasons for the higher HP ratings of the SM Trans 376 and 390 hp 428s other then the better Exh Manifolds !

We need to get our hands on more factory parts manules like you have Rocky, but for many other years!

[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...

[4zpeed]

Outstanding thread Rocky, the level of participation here is what makes it possible to decipher and rediscover information such as this.

May recruit some further contributions to your statistics here should this be made readily available, things of this nature require numbers and time.

steve25
All of this new info may end up having a deep impact on the 67 show car owners!

Invaluable information for some in the tribe indeed.


Thanks,
Frank

[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?

[Rocky Rotella]

Originally Posted by 4zpeed

Outstanding thread Rocky, the level of participation here is what makes it possible to decipher and rediscover information such as this.

May recruit some further contributions to your statistics here should this be made readily available, things of this nature require numbers and time.

steve25
All of this new info may end up having a deep impact on the 67 show car owners!

Invaluable information for some in the tribe indeed.


Thanks,
Frank

Thank you, Frank.

I truly enjoy the detective work that it takes to notice and solve these types of things!

[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?

[67GP428]

My '67 GP 428 WG 4 speed. No markings. Cleaned off the old paint, that's why a little different color. Scott