[njsteve]

Were there two versions of the 7F6 455HO cylinder head for the 1972 model year? I have seen heads with this strange inset area between the intake runners and other sets with a flat normal mounting face where the intake gasket mates up. The ones on my car are the flat straight-across style (second photo). I am wondering how in the world the intake gasket was supposed to seal with a 2-inch gap under the gasket?

[Lloyd-TX]

Hey Steve:

Interesting subject. If you do a search, you'll probably find at least three threads on here pertaining to those 7F6 head intake surface "scallops" (for lack of a better term).

I have owned several pairs of 7F6 heads. It appears that there was a running change somewhere around the same time that the intake manifold casting number was changed (485630 to 488945). In my research on this subject, it appears most likely around January of 1972 the change took place, as all of my '71-dated sets have had the scallops, and all of my '72-dated sets have NOT have those scallops.

I've posted here about this before, and spoken with numerous long-time Pontiac experts in the past, with no explanation yet.

Here is my best guess:

I believe that Pontiac engineers were originally planning on keeping the '71-style single-booster Q-jet for the '72 HO's, and were attempting to smooth out the intake manifold pulses to each primary venturi. With these scallops in place, each intake port would have a slight "draw" upon it's neighboring port, thus assisting the signal to the primary venturis. As you know, each port in each pair on an OEM dual plane intake pulls from the opposite side of the carburetor.

Since Pontiac did not use the "800 CFM" single booster Q-jet in 1972 after al, I suppose that it was decided to eliminate the scallop after the first few runs of cylinder heads were produced?

Who knows, and this is simply an educated guess on my part.

I'd sure like to know the real story on this from a Pontiac engineer - if we can ever find out!

[Larry Navarro]

nevermind....Lloyd beat me to it.

[njsteve]

Wow, it's like I walked in to Cheers and Cliff Clavin just rendered one of his famous soliloquoys. You just left out the: "As a matter of fact there Normy, the Pontiac 7F6 cylinder head...."

That's why I love this site. It's full of Normy's and Cliffs. I guess I am a Normy today.
;-)

[Lloyd-TX]

Originally Posted by njsteve

Wow, it's like I walked in to Cheers and Cliff Clavin just rendered one of his famous soliloquoys. You just left out the: "As a matter of fact there Normy, the Pontiac 7F6 cylinder head...."

That's why I love this site. It's full of Normy's and Cliffs. I guess I am a Normy today.
;-)

Sorry to get so long-winded there, Steve. It's just that I am so involved on the '72 HO engines, and this is the one mystery that has escaped a satisfactory explanation to this day.

[Formulabruce]

I do not dispute Lloyd, however there was also mid year changes in the emissions in 72 that required a different vacume structure, and tighter controls on vacum, spark timing and off idle performance. I think its possible the missing scallops also may have been necessary for emissions, which may play into the carb change mentioned by Lloyd. My 2 cents.

[RicksGTO]

mine are dated J011 and have the scallop. I started reading about them after pulling the motor and thinking something had gone amiss with a porting burr somewhere back down the line but was relieved to find it was normal. I guess since the scallop doesn't go all the way to the top or bottom of the port there is no issue with sealing, just kind of a controlled internal leak or draw as Lloyd said.

[1971WARBIRD]

you guys have done a lot more research than i have,but this is what i was told once.
the ones that were smooth were later replacement heads.now that you have said you have seen 72 dated heads without the cuts i'm back to scratching my head again.reason i try to keep an open mind.

[The Boss]

Originally Posted by njsteve

Wow, it's like I walked in to Cheers and Cliff Clavin just rendered one of his famous soliloquoys. You just left out the: "As a matter of fact there Normy, the Pontiac 7F6 cylinder head...."

That's why I love this site. It's full of Normy's and Cliffs. I guess I am a Normy today.
;-)

Can I get a beer over here?

Good stuff here guys!

[weranc55]

Those pics Nj has are of my heads that are on ebay. I also thought it was strange about the intake ports but they ran just fine on the motor. If anyone needs a 72 ho intake I'm also selling one on ebay. Lloyd thanks for the info on the heads.

[GonicGM]

Interesting!

Without first reading the thread, I would have first guessed pattern flaws on the casting. However, the castings are too consistent to really suggest this.

[johnta1]

What I think is strange is the early 455 heads in 1972 all had the recess, the 7D4 7L5 and the HO 7F6.

When they eliminated the recess they changed the head casting numbers to 7M4 but didn't change the HO head casting number.

[Lloyd-TX]

F-Bruce - there were no mid-year calibration changes in the 1972 MY that I am aware of. Carb #'s and jetting, distributor #'s, and vacuum hose routing remained consistent throughout the year, AFAIK. Now - 1973 is another whole story, as Pontiac got into BIG trouble with the feds over their EGR "timing" and flow.

Warbird - the scallops were indeed eliminated from the 7F6 head castings during the model year run. I've had at least two pairs which were quite obviously production heads, one pair had A**2 casting dates and the other pair had C**2 dates.

weranc55 - please post or e-mail me the casting dates on those heads. As long as I'm working on my WW5 database, I might as well keep a file on 7F6 heads, noting casting dates and those scalloped intake ports. TIA. Also, shoot me some pics or post a link to your auction for the intake. Is the crossover for sale as well?

I'd appreciate that info from any and all who have loose heads and/or their intake manifolds removed.

[weranc55]

http://cgi.ebay.com/ebaymotors/ws/eB...175046974&rd=1

Thats the link to the intake and it ends tommorow and comes with the crossover. I can not get to the date code. It seems like part of the crossover is riveted to the intake. I dont know if its factory but it looks like it could be.

I171 on both heads.

[Jim Robertson]

Both sets of my heads have divider flush with surface. I101 and C142. The I101 dated heads are in question. Flange on both heads is approximately .060" thinner than the
C142 heads. My guess is milling has occured on the I101s. How deep is the recess on an untouched head? In other words how much milling would it take to "remove" the recess?
Jim

[Lloyd-TX]

Originally Posted by Jim Robertson

Both sets of my heads have divider flush with surface. I101 and C142. The I101 dated heads are in question. Flange on both heads is approximately .060" thinner than the
C142 heads. My guess is milling has occured on the I101s. How deep is the recess on an untouched head? In other words how much milling would it take to "remove" the recess?
Jim

Hey Jim:

.060" would indeed take care of those scallops, and every set of '71 dated 7F6 heads I've laid eyes on has had them.

So, your two sets definitely follow the pattern I've seen.

Thanks for the info.

[Lloyd-TX]

Originally Posted by johnta1

What I think is strange is the early 455 heads in 1972 all had the recess, the 7D4 7L5 and the HO 7F6.

When they eliminated the recess they changed the head casting numbers to 7M4 but didn't change the HO head casting number.

That's very interesting info, John. I think that I had also heard that before, but it's been a while.

Kinda shoots my single booster carb theory down the commode, doesn't it? I highly doubt that Pontiac was planning on an 800 CFM carb on a Grand Ville, LOL!

[PB]

I noticed my heads were like this last summer when I rebuilt my engine. Had I caught it BEFORE I sent them to the machine shop, I would have had them filled in with epoxy. If I get enough gumption, I will pull mine off and get it done sometime. I think there is a performance issue if this is not done. My 72 has never sounded quite right...like you'd think a gto should and I think this gap messes up the fuel/air mix just a bit to make it sound off kilter and not get all the max performance from the heads.

The heads I bought last year are Jan - Feb dated IIRC and don't have the scoop out.

[Lloyd-TX]

Originally Posted by PB

I noticed my heads were like this last summer when I rebuilt my engine. Had I caught it BEFORE I sent them to the machine shop, I would have had them filled in with epoxy. If I get enough gumption, I will pull mine off and get it done sometime. I think there is a performance issue if this is not done. My 72 has never sounded quite right...like you'd think a gto should and I think this gap messes up the fuel/air mix just a bit to make it sound off kilter and not get all the max performance from the heads.

The heads I bought last year are Jan - Feb dated IIRC and don't have the scoop out.

Thanks for the info, Pat.

When you have a chance, shoot me the casting dates on both of your pairs of heads for my database.

Thanks, my friend.

[The Boss]

Lloyd, the set on the car are both J011 and I have at least one more set in storage, but may not be able to get to them. Not sure what mine look like inside, but I'd assume they have the notches. I also have the 640 intake.