[Progolfer]

Hey Rocky - I posted some pics Friday night but for some reason the post didn't show up. I have 2 - 670 heads with Z on them. At first I thought they were from a WS Block HO engine that I purchased 35+ years ago. They still have the stock exhaust manifolds on them which makes me think they are standard 335 hp heads K066 & K146. Do you think these could be the original heads from the 67 GTO. I am guessing the date codes are November 6, 66 and November 14, 66. Which matches the build of the car as we have discussed in the past :-) Hope this helps.

Frank

[77poncho]

Originally Posted by steve25

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

it was pretty late last night when i took that pic.. yeah i see what you mean almost looks like 0.. i most likely with be having these heads tanked soon to clean up and then to decide what to do with them.

[ANDYA]

Rocky, there is a member here on the forums that goes by Aluminum Chief. I believe he has two original ram air 67 GTO's ( at least he did at one time) and may be able to answer some questions. Also, member Perry Kaiser has a ram air GTO and could possibly help. I don't have any way of contacting them but hopefully they will see this thread and respond. Then again if Nunzi says there was an X marked on the heads I would believe him. He has seen more than any of us will ever see when it comes to Pontiacs.

[steve25]

Something rang a bell in regards to these 670 heads and 428 motors!

I went back and looked in Pete McCarthys first book and on page 39 the 376 hp 428 is stated as coming with two different valve spring set ups, one for the standard Trans cars that have Exh springs with a higher pressure , and then a set up for the auto trans cars.

The factory would have needed a way to differentiate between these assembled heads and maybe that's where the Z and the o stampings come into play?

The 360 hp 428 seems to use the same pressure springs across the board between the standard Trans and auto Trans cars which would lead me to believe that both these 360 hp 428 motors and the non RA 400 motors would get the same springs and hence the same stampings .....?

Now to prove this out and then prove out which stamping code goes with the 376 Hp standard Trans 428.

[Held for Ransom]

Could the Z refer to emissions and the accepted use in California cars?

[steve25]

Well one way to prove that would be for example if the Z stamped heads in Rockys photos had there end of Head air injection galley plugs in or out, and my Z stamped heads still have there factory plugs in the end of them !
On we go to prove out what these stampings mean!

[PAUL K]

Originally Posted by ANDYA

Rocky, there is a member here on the forums that goes by Aluminum Chief. I believe he has two original ram air 67 GTO's ( at least he did at one time) and may be able to answer some questions. Also, member Perry Kaiser has a ram air GTO and could possibly help. I don't have any way of contacting them but hopefully they will see this thread and respond. Then again if Nunzi says there was an X marked on the heads I would believe him. He has seen more than any of us will ever see when it comes to Pontiacs.

I gave Aluminum Chief a heads up. Interesting to see what information he may provide.

[Progolfer]

1967 GTO Heads with Z code

[Rocky Rotella]

Great participation, guys!

Steve, I was wondering the same thing as you noted about valve springs. I wonder what's unique about the 9788066 cylinder head that I spoke of in the original post?

[Rocky Rotella]

Originally Posted by Progolfer

Hey Rocky - I posted some pics Friday night but for some reason the post didn't show up. I have 2 - 670 heads with Z on them. At first I thought they were from a WS Block HO engine that I purchased 35+ years ago. They still have the stock exhaust manifolds on them which makes me think they are standard 335 hp heads K066 & K146. Do you think these could be the original heads from the 67 GTO. I am guessing the date codes are November 6, 66 and November 14, 66. Which matches the build of the car as we have discussed in the past :-) Hope this helps.

Frank

Frank,

I believe the 1967 model year was the only year that "I" was void in the cast date sequence. That would make your K-dated cylinder heads October 6 and 14, respectively, and that makes it much more logical that they could be installed on an October-built '67 GTO.

I would LOVE to believe that they are original to your GTO, but it was built on October 20 at the Kansas City plant. I would think that the timeline of the 670s being cast, machined, assembled, installed on an engine all at the Pontiac, Michigan plant and then shipped by train to KC and installed in a vehicle within 6 days would seem extremely tight. It's certainly possible, however!

[Progolfer]

Originally Posted by Rocky Rotella

Frank,

I believe the 1967 model year was the only year that "I" was void in the cast date sequence. That would make your K-dated cylinder heads October 6 and 14, respectively, and that makes it much more logical that they could be installed on an October-built '67 GTO.

I would LOVE to believe that they are original to your GTO, but it was built on October 20 at the Kansas City plant. I would think that the timeline of the 670s being cast, machined, assembled, installed on an engine all at the Pontiac, Michigan plant and then shipped by train to KC and installed in a vehicle within 6 days would seem extremely tight. It's certainly possible, however!

That makes sense and would make it a tight timeline - I hate to say it's been too long and too many moves to remember which heads these are. If these are the heads off of the WS engine that I bought, would the WS engine have had std exhaust manifolds or would it have had the ramair manifolds?

[Aluminum Chief]

My 67 HO 4 speed car has a Z dated A047 and my 67 Ram Air 4 speed car is up on a lift with a car under it, I will try and get to that in the morning. KC

[242177P]

Starting to see a trend here....

H256 and H266, both stamped with an O. YS
K036 and K046, both stamped with an O. YZ

[steve25]

I had another Bell go off last night so I pulled out Pete's 2 books, and here what I come up with.

In his first book it list for 1967 a 360 hp and 376 hp 428, the 360 hp motor having a 10.5 comp and the 376 hp motor as being 10.75.

Well this brings up the question of if the
670 heads are all 72 to 73 CCs, then how did the compression change come about?

If you look in this same book at the detail listings on the 68 428 motors you will find that the 375 hp 428 used a .050" head gasket and the 390 hp motor used a .042" head gasket, and I believe the X stamping on the head is used to differentiate a assembled motor with the highest compression ratio as when put into inventory the factory needed a way to know how the motor was built.


I think the factory did the same gasket thing in 67 , but the book does not list such.

Now here's why I believe such!

In Pete's second book in the section on the early SD motor you will find on page 169 some shots of a 61 to 62 177 head.

In Pete's discription of the clearly marked stampings on the head he notes that the head was for a 10.75 motor with HD valve springs.

The X he states denoted the 10.75 comp and O stamping denotes the HD valve springs.

If we assume that 5 years down the road in 67 that the engineers and or the factory used the same stamping code then we now know what the X and O stamping means and then like I posted the Z stamping indicates standard valve springs for that year, or Heads that are not fully set up for air injection, I think the latter!

My 670 heads came off a GP here in the east, so no air injection.

What do you folks think?

[steve25]

Where would we be in this hobby without Pete's 2 books ?

Anyone have or know anyone with stock fully assembled 67 400s or 376 or 390 hp 428 motors for a autopsy?

[Old Goat Racer]

A friend of mine in St. Louis has a 67 HO 4-speed with air GTO. He says there are no markings on the dime size pad.

[steve25]

It would be good to find out the casting dates on those HO heads.

[Old Goat Racer]

He said 11-18-66

[steve25]

Thanks!

[Rocky Rotella]

With the assistance of everyone involved, I believe we are starting to unravel this mystery a bit.

I took the chance this weekend to pore over my May 1968 and March 1969 parts manuals to compare everything connected to the 1967 670 casting. I found some very interesting information that may point us in a direction where we can eventually piece this puzzle together. Keep in mind, Ram Air-spec 670s are excluded below.

Background

There were other 400 applications in 1967, but it’s generally well understood that the 670 was used on Grand Prix’s 400 4bbl, the various 400 4bbls available in the Firebird and GTO, the base 428 4bbl (360 hp), and the 428 H.O. (376 hp). It’s these latter applications that may hold the key to piecing this together.

Cylinder Heads

The parts manuals show that two different 670 castings were used during the 1967 model year. Both were application dependent.

• 9788066- Cylinder Head was specific to Grand Prix’s 400 4bbl and the base 428 4bbl (360 hp).
• 9788067- Cylinder Head was specific to GTO and Firebird 400, and the 428 H.O.

Intake and Exhaust Valves

The parts manuals show that a single exhaust valve was used in the 670. The 1.77-inch number-9787584 Exhaust Valve was common to all applications. However, two intake valves were used.

• 9787587- Intake was specific to Grand Prix’s 400 4bbl and base 428 4bbl.
• 9789725- Intake was specific to GTO and Firebird 400, and 428 H.O.

Obviously both intake valves are 2.11-inch diameter. I believe both were constructed of SAE-1041 alloy with aluminum coated faces, but that 9789725 was further treated to a chrome-plated stem for improved performance.

Valve Springs

Pontiac used the same outer and inner valves springs on the intake and exhaust valves to arrive at the required spring pressure for a given combination. The parts manual shows that 9779009-Outer spring was common to all 670 applications. The Inner valve springs, however, were application dependent.

• 9779008- Inner was common to Grand Prix’s 400 4bbl and the base 428 4bbl regardless of transmission. It was also common to GTO and Firebird 400, and 428 H.O. with AUTO trans.
• 9781476- Inner (with increased rate) was specified to GTO and Firebird 400, and 428 H.O. with MANUAL trans.

Cylinder Head Gaskets

The parts manuals show two different cylinder head gaskets depending upon the application.

• 9787642 has a nominal thickness of approximately .052-inch. Usage was specific to Grand Prix’s 400 4bbl and base 428 4bbl.
• 9785654 has a nominal thickness of approximately .042-inch. Usage was specific to GTO and Firebird 400, and 428 H.O.



So what does all this tell us? It suggests a few different scenarios.

1) Since two different 670 cylinder head castings (9788066 vs 9788067), we can surmise that there had so be some type of special machining that differentiated the two cylinder heads that ultimately required a different part number. Since two intake valves (9787587 vs 9789725) were also used, based stated application usage it’s quite likely that intake valve guide clearance on 9788066 was compatible with the basic stem finish of the 9787587 valve, and that 9788067 included additional intake guide clearance (or a slightly larger overall guide diameter) to accommodate the chrome-plated stem of 9789725. There absolutely had to be a way for Pontiac to identify this in service.

2) The varying cylinder head gasket thickness was a way to give 428 H.O. a compression ratio boost when compared to the base 428 4bbl. I believe the advertised compression ratio of 10.75:1 and 10.5:1, respectively, was overstated. The actual compression ratio of either should roughly .5 less. The .052-inch gasket in Grand Prix’s 400 4bbl and base 428 4bbl applications gave buyers engines that were less sensitive to fuel octane, and possibly more user-friendly on the street.

3) With the help of a 1967 A-car Engine Assembly chart that lists the components comprising every A-car engine produced that year, I can make a few accurate statements. All GTO 400s included the 400 Ram Air utilized cylinder head gasket 9785654 and actual compression ratio was nearer to 10.2:1 than the advertised ratio of 10.75:1. The chart also clearly lists two different COMPLETE ASSEMBLY part numbers for the 670. 9787603 is specific to GTO 400’s with AUTO trans while 9786708 is specific to GTO 400’s with MANUAL trans. Undoubtedly, the differences were directly related to the valve springs. (We can surmise that the 428 H.O. followed suit.) Pontiac had to have a way to visually identify these.

4) Pontiac believed that buyers opting for non-H.O. 421 (in 1966) and 428 4bbl (1967-1969) backed by a MANUAL trans (as well as Grand Prix buyers opting for standard 400 4-speed) were purposely selecting those combinations for price and low RPM operation. With high RPM operation an unlikely concern, these particular applications used the same valve springs as those specified with the automatic.

With all this said and what’s been contributed so far, we may be closer to understanding the 670 differences that might require such stampings as “O”, “Z”, and Ram Air’s “X” on the 670 castings. Is the following possible?

• “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?