716 heads
 

hi just got a set of 716s heads can some one tell me what the x over the frees plug means and the xo over the casting number in the head thank you brody

I think you mistyped - should be 76?

The 'XO' are stamped?

The 'O' if it is stamped usually meant stiffer valve springs.
The 'X' if it is stamped was for higher compression ratio.
(smaller chamber)

Have a picture of them?

:)

no the heads are 716s with a date f14 64 thanks thou for getting back to me

Never heard of added coding on the '64 716 heads. Maybe we'll learn something new on this thread!

There must have been a way to ID the 421 heads from 389 heads used on GTO's. The chambers were quite different in volume. Maybe that's what the X's and O's mean.

They were used on 389 and 421 so maybe chamber size?

In the previous years, what I wrote is how they differentiate the heads.

I did not think they did it after 63, but they could have.
I tried looking through the tech bulletins but haven't found any for 64.
(doesn't mean it didn't happen)

Seems I remember them doing it for the higher performance heads in a later year (1966?)?

The 'X' on the front of the head, is it a stamped 'X' or a casting?

:)

the casting x on the front of the head is on a pad and inverted so its cast in the pad thanks for all the in put

That is just part of the casting/process.
Doesn't mean anything.

:)

Does anybody have a pair of these heads or know where to find some. If so please message me Thank you!

Does anyone know how Pontiac identified heads used on two different-sized engines---like these '64 716 heads, '65 77 heads, '66 093 heads, and '67 670 heads, and others? There had to be a code since cc's would be different for the two engine displacements.

Dick,also 69 48 heads for a 350HO and a 400.Tom

I've always wondered about the 48 heads as Tom said.
The others, I wonder if the pistons had more of a chamfer on them to make the CR come out right?

:confused:

I do know the factory did use diff thickness head gaskets for some builds!Tom

The 421 used pistons with deeper valve reliefs to keep the compression ratio on par with the 389s, much in the same way that 428s used dished pistons to match the same compression ratio as the smaller 400 engines that shared the same heads.

Definitely a big difference in valve relief volume between the 421 and 389 pistons, very likely a 6cc difference between the two.

Pictured below are factory pistons that came from 1964 421 and 389 engines.

http://i137.photobucket.com/albums/q...h/DSC03699.jpg

http://i137.photobucket.com/albums/q...h/DSC03698.jpg

63 389GTO/421HO 9770716 9770716 9770981 Press 1.92 1.66 68 (72)

His are dated f14, which is for a late 1964 car.
(June1, 1964)

I still haven't found my info on the head stamps.
:(

I believe McCarthy wrote of it in his book, also.

:)

"The '64 9770716 GTO (and '63 -'64 421 HO) head has a 17 degree valve angle and uses 1.92"/1.66" valves, these were the big-valve Pontiac performance street heads of their time (standard 389 heads up through '64 used 1.88"/1.60" valves). The early offset chamber placement doesn't allow the practical use of valves any larger than the 2.02"/1.76" valve sizes used in the race-oriented '62 -'63 421 Super-Duty heads."

http://i22.photobucket.com/albums/b3...ps06e8eac5.jpg
http://i22.photobucket.com/albums/b3...psa573338b.jpg
http://i22.photobucket.com/albums/b3...psd47b1519.jpg

Mescabug, is that your head?
If so, what engine did it come off of?

:)

Yes, these 9770716 casting numbers were used in '63 and '64. Was this the only instance of Pontiac using the same head casting for more than one year?

Did any Tripower '63 421's use the 9775088 intake casting? Or, did they use the casting number 9770275 intake like the '63 389's used?

From my experience, Tripower intakes had different casting numbers for each year from '57 through '66, even though some were very similar--notably '61 and '62.

As far as I know the 63 421 used the '275 intake.
(389 and 421 both)

:)

I think you're right. It's hard to believe they used that flat 275 intake on the Tripower 421 HO.

Several years ago I tried to collect info about the X & O stampings on the '63/'64 9770716 Head castings.

Never was able to collect enough data to come to a conclusion.

I did speculate based on what I did find and have mostly forgotten if any data contradicted what I came to believe.

It starts by the knowledge that PMD used these Heads for the '64 421HO and also for various '64 389 applications, including the '64 GTO.

All had an advertised 10.75 cr. The advertised cr did not especially match reality, but it made no sense to me that the 421HO Heads could be used directly on a 389 and yield a higher cr than the 10.5 cr 9773345 "regular" 389 Heads without some milling.

b-man, you may be right about the valve relief accounting for the chamber volume difference.

But I was never very "satisfied" by the various explanations that suggested larger vol reliefs used for the 421 pistons and/or head gasket thickness differences.

Especially since the Heads exhibited the stampings.

Then there was the fact that the early '64 GTO Heads made use of the lighter duty Valve Springs, switching to the 421HO Valve Springs around Nov. '63.

I have a pre-Nov Head example which I believe was original to my own Nov. built GTO which was stamped X X and a later '64 Head that was stamped X O (not original to my GTO).

My speculation is that the early X X Head indicated a Head milled for 389 use with lighter Valve Springs.

And the later X O Head indicated a Head milled for 389 use with heavy duty (421HO) Valve Springs.

What I was never able to find were examples of 9770716 Heads known to be original to a '64 421HO to see how they may have been stamped.

Logic suggested that they wouldn't be stamped at all, only those reserved for 389 use would have needed to be specially milled and given secondary stamps to identify them.

Also, IIRC, the 9770716 Head was only used for the 421HO in '63, so no reason for any stamp codes on them (if they only came in one flavor), but finding examples from '63 proved impossible for me.

Just never could prove whether my speculation was valid.

The '65 77 and '66 093 Heads also had shared 389/421 usage too but I never heard of anybody claiming to have seen secondary stamped codes on any of them.

The '64 X and O stampings can be found on the dime sized bosses on the center exhaust ports.

The biggest problem is corrosion of the casting which makes detection of secondary stamp codes difficult.

I have a set of 421 HO 716 heads that are original my 1964 421 HO 45B block.

I will try to get a look at the heads this weekend to check for any stampings.

The head pictured at the bottom is mine, it was pulled off of a '64 389. The block had no stamping to identify it as it had been ground off by a previous owner, but it must have been either a GTO block or a Tri-Power big car block.

I will try to look for any stampings on them this weekend.

Well, after all these years, I thought I new my car pretty well, BUT. I just went to the garage, knowing I wouldn't find any markings but I did. One head has a distinct X on the right side of the dime. Left side of the dime is pretty uneven and I can't make out anything. By the X being on the right, guess I have XX head, which I think I should from this discussion. They are original April 64 heads. "Bill"!

1964 421 HO 9770716 head - X and X stamped:

http://i137.photobucket.com/albums/q...O/DSC01586.jpg

421 HO head date code - I 30 3 September 30, 1963

http://i137.photobucket.com/albums/q...O/DSC01587.jpg

1964 421 HO block date code - I 27 3 September 27, 1963

http://i137.photobucket.com/albums/q.../P10100062.jpg

1964 421 HO block code - 45B 370 HP manual transmission

http://i137.photobucket.com/albums/q...10100043-1.jpg

1964 389 GTO (or big Pontiac 389 Tri-Power) 9770716 head - X and O stamped:

http://i137.photobucket.com/albums/q...e/DSC01588.jpg

389 head date code - B 14 4 February 14, 1964

http://i137.photobucket.com/albums/q...e/DSC01589.jpg

1964 GTO 389 (or big Pontiac 389 Tri-Power) block date code - B 18 4 February 18, 1964

http://i137.photobucket.com/albums/q...e/DSC03480.jpg

Bart,any chance you can CC the xx and the xo heads?Tom

Tom,

I won't be able to do it any time soon. I don't have the tools to do it here. Both sets appear to be untouched.

Bart

Thats why it would be a good pair to check.Im betting they are diff.Tom

b-man, that is excellent input. Just not sure what I can make of it. :)

I will also be curious if there is a chamber vol. difference.

I went back to check some of my notes from years ago. My heads aren't accessible at the moment, so relying somewhat on memory.

First off, the original engine in my '64 GTO was EUN around 101000.

The valve spring change was made at EUN 190810 (somewhat later than I was remembering the other day).

My Head marked XX has a Jxx3 date code as best I remember it. This is the one that I believe was original (at least by cast date, it seemed legit). The Head marked XO has a Exx4 date code, again from memory. The mismatch was consistent with some known history of the car, although not proof positive that the early Head was original to the original engine.

I also reviewed a discussion I had several years ago with Keith Seymore about an early mag article he shared with me. It was a puff piece about the '64 GTO in Hot Rod.

In it, it claimed the Heads were the same as used in the 421HO, and claimed the difference in valve relief vol enabled the 389 to achieve the same cr as the 421, the chamber vol was claimed to be 67 cc in either case. So the claim was being made in '64. No mention of any factory milling for the GTO heads. So whoever provided the info for that article was unaware that the Head was being milled by PMD for 389 use or it truly wasn't being done.

Another article from Popular Hot Rodding that Keith shared with me stated that Royal was typically seeing these heads come in 5-6 ccs over the 67 cc spec, so Royal was milling them for increased cr.

Assuming my early Head is in fact original to my 389 GTO engine and is marked the same as your early 421HO Head example, it would seem that there is some other reason for the change from the XX marking to the XO marking.

It occurs to me that the known change was to the Valve Springs for the GTO Heads starting with EUN 190810 and perhaps the XO came into use at that point. However, to my knowledge, the 421HO did not use the lighter springs at any time, so it would make no sense that later 389 Heads would be marked differently than early 421HO Heads UNLESS there is some difference between them.

Possibly my XX Head is ALSO not original to my GTO. Bill didn't get a clear read of the marking on his late Heads, but if I understand what he wrote, he has an X on the right side boss. So presumably his are marked XX. And they are April Heads, long after EUN 190810.

Your known Feb 389 Head and my May Head (unknown origin) are both marked XO.

So you can see how the data for the stamped markings gets to be pretty confounding.

I'm sure the 64 GTO and the 421 HO used the same cam and we know the same heads so would assume had the same springs.Tom

1964 GTO - 524009 cam.

1964 421 Tri-Power with standard exhaust manifolds - 524009 cam.

1964 421 HO Tri-Power with long-branch HO exhaust manifolds - 9770543 cam.

The 524009 cam has the same profile as the 9779067 cam.

The 9770543 cam has the same profile as the 9779068 cam.

Looking at the valve spring specs listed in the John Angeles/Pete McCarthy Racer's & High Performance Handbook it appears all the above listed engines used the same exact valve springs.

No piston valve notch/relief volumes were listed in the 1964 engine tables, but in the 1965 tables all 389 engines had 4.0cc valve notches and all 421 engines had 10.0cc valve notches.

1964 Pontiac Engine Chart:

http://forums.maxperformanceinc.com/...1&d=1382896403



1964 Tempest Engine Chart:

http://forums.maxperformanceinc.com/...1&d=1382896403

The HO used a 'HD Dual Spring' instead of the dual spring which is different than the normal single spring used on most engines.

:)

Tom, this does NOT appear to have been true at the start of the year until EUN 190810, which would have been assembled some time around late Dec. '63.

Pontiac documentation exists which details the valve spring change for the GTO Head usage, no mention that it affected the 421HO Head usage.

If anybody wants, I can scan the document. It is also referred to in the '66 MPC for Valve Springs with the EUN break point noted.

b-man, would the '65 piston valve reliefs be same as '64? That 6 cc difference is a lot more than I would have guessed, but it seems to confirm that the cr was "controlled" by the valve relief difference between the 389 and 421.

But that still leaves the XX and XO stamp markings to be explained.

I have owned a lot of 716s over the years and all have been dual springs and I never put them on a spring checker.I just thought they were the same.I never payed any attention to the XX or XO codes on them either.I would be interested in the CCs of both untouched heads just for snicks.Tom

Here are a couple pics from McCarthy's book:

http://forums.maxperformanceinc.com/...1&d=1382966027


http://forums.maxperformanceinc.com/...1&d=1382966027


I still can't find the bulletin or whatever it was that had the info on how/why these were stamped this way.
:(

Someday, maybe.

Anyway, I think this was kind of a standard practice doing it this way, just not sure when they ended it.
(probably when they quit putting that flat boss on the center exhaust ports?)

Later years like from 73 on they stamped the ID's on the upright boss like the 6X - 4, etc.

:)

Didnt saw your posts.

Found them on my computer. I probably got them from the forum here.

Like b-man said, I think its his.

I also am curious to know about the ccs, although I'm leaning toward the likelihood that they were machined the same.

I do not recall how the attached pages were published, I'm thinking something like a News Flash, maybe somebody here knows for sure.

The purpose was to provide the necessary info for the unique features of the GTO engine, and it is here where they comment about the change in springs for the GTO engine.

As you can see, they were all dual springs. But the early production GTO Heads used the same standard springs used for the 10.5 cr 389 and the 326 Tempest Heads.

Later production was switched so that the GTO Heads used the same Heavy Duty Springs that were specified for the 421HO application in '63 and '64.

I have also relied on what McCarthy wrote about the meaning of the X and O stampings on pre-'64 Heads.

But unless the known original Heads b-man has from a '64 421HO were incorrectly selected at Engine Assembly, I would NOT have expected them to show XX as if to indicate standard springs (or at least, NOT HD springs).

And if Bill Ryder's April Heads are really stamped XX, long after the GTO valve springs were switched to the HD, that also makes no sense.

And I have a May Head stamped XO. Certainly by that date, there should have only been one flavor of the 9770716 Head.

It should be obvious that the original p/n for the GTO Head Assembly was NOT 9770981.

Maybe somebody has an early unrevised '64 MPC that lists the original GTO Head Assembly p/n.

My guess is that it would have been p/n 9774767.

The '64 10.5 cr 389 & 421 Head and Tempest 2 bbl 326 Head (8.6 cr) was p/n 9774766.

The '64 10.5 cr Tempest 4 bbl 326 Head was p/n 9774768.

Head Assembly p/ns were often issued in consecutive p/n sequence so the "missing" p/n 9774767 would logically have been the GTO Head with standard Valve Springs.

And then obsoleted when the GTO was switched to the HD Valve Springs.

As an aside, according to the MPC, there was no special Head Gasket used for the GTO or 421HO. All of them specified p/n 542973 for service, same as for all '63-'66 V8 applications.

It occurs to me that when the early GTO Head shared the same casting as the 421HO Head, but specified different Valve Springs, there may have been some Engine Assembly confusion.

That could be the reason b-man's 421HO example shows the XX code. Perhaps that Head was intended for an early GTO engine but mistakenly assembled on a 421HO engine?

Bill Ryder or anybody else that has a set of known original GTO Heads, it would be useful to see if they are stamped XX or XO and what dates are on them.

Same for any later 421HO Heads.

And for that matter, would be interesting to know if the '63 421HO Heads have any stamped markings.

Unfortunately, I think I am right back where I wound up several years ago. Contradictory evidence even given the fact that the early '64 GTO Head was known to be different in some respect from the '63/'64 421HO Head and later the '64 GTO used the same Head as the '63/'64 421HO. Just can't establish what the XX and XO was supposed to signify.

Cool docs, John.

:)

If the 'Eng No. 190810' is the Motor Unit Number/Engine Unit Number, what would the approximate date be for them?
(from the valve spring info on last pic)

Dec. 63/Jan.64?

:confused:

John, see pg. 2, EUN 190810 was assembled 12-19-63.

That break point date is consistent with my '64 engine log;

EUN 163xxx has a block cast date of K283
EUN 203xxx has a block cast date of L233
EUN 225xxx has a block cast date of A64

Cast dates can vary but generally, I would say that 9770716 Heads cast after about L153 should generally all have gotten the HD valve springs at Head assembly assuming they stopped using the standard valve springs on or about 12-19-63 and on that date most of the Head castings would have been cast L153 or later.

I imagine some earlier castings would have been assembled after the break point, but not a lot. Every now and then, I found a block cast much, much earlier than the engine assembly date (established by the EUN). So it is possible that a rare Sept, Oct, or Nov Head casting wasn't assembled until after the change was made. But for sure, you should never find a Head cast after 12-19-63 assembled with the standard springs.

If the stamped codes indicate the springs used for the Head assembly, you would not find the standard spring stamp code on a later dated Head casting.

My assumption is that the XX would indicate the standard springs. So I would not expect XX stamped on later dated Head castings. If Bill's April Heads are stamped XX, that would blow that assumption up.

I never recorded Head cast dates for my log (since it is under the valve cover), just the block cast date. But you can see that the block cast dates were usually within a few days or less of the date the engine was assembled. From what I understand, the Heads were typically cast very close to the date of the block in many/most cases. So that is why I suggest L153 would be a pretty good guess of the break point.

Sorry, Haven't paid any attention for the weekend. I need to correct myself. Originally I thought the X and O was on the same boss, not one on each. So what I said before is not correct.
I've tried to upload a picture with no success so I will explain:
My X is on the right hand side of the LEFT dime sized boss. Not centered. The right hand side dime sized boss is almost empty with just a small arc on the top side about 2 o'clock position. Could be part of an O. I can't say for sure. The other head is completely void of marks. SORRY if I got you going in the wrong direction!!!!!!!!!!!! "Bill"!
Just found the head pics I took in 1990. Both heads date code is C254.

Bill, thanks for clarifying your stamp marks.

The fly in the ointment would appear to be the early XX stamped Heads.

If all late 9770716 Heads were the same and if at least some of them were stamped XO (notwithstanding Bill's example lacking any stamped marks and his example that was stamped off center so that the marks aren't clearly interpreted), then logically the early heads stamped XX must have been intended for the 389 GTO (the '64 10.75 cr 389 big car tri-power engines are way too rare to know whether they shared the GTO Heads or the 421HO Heads early year but since there is no mention of early & late valve spring choices for this big car engine, I suspect it should have gotten the 421HO Heads and not the GTO Heads for the entire year).

But the only known 421HO example is b-man's and it is stamped XX. Either my interpretation is wrong or else that early '64 421HO engine was incorrectly assembled with the GTO Heads having standard valve springs.

b-man, if you have the tools to check it and if the valve springs on your 421HO Heads are still the originals, you could measure the wire dia. for the inner and outer springs to see if they match the standard or HD spring dimensions.

That might help point to a conclusion.

Follow up to my own earlier post with the Engine Spec pages, this WAS published as a News Flash in case anybody wants to hunt for it.

News Flash No. 64-95, dated 5-1-64.

The 421 HO heads stamped 'XX' have the standard valve springs, .162" outer and .120" inner wire diameters.

The 389 GTO heads stamped 'XO' have the HD springs, .170" outer and .141" inner wire diameters.

I used some dial calipers to measure them.

Everything looks to be original on both sets of 9770716 heads.

b-man, that is excellent and I think is pretty compelling "proof" of the actual difference between the XO and XX heads.

Since the early GTO Heads are the only version identified in the published PMD documents that were supposed to have used the standard springs, my guess is that your 421HO was built with the XX Heads by mistake. No indication that the 421HO Heads were ever supposed to use the standard springs and given that they were a carryover from '63, very doubtful the standard springs were intended for the 421HO Heads.

It even occurs to me that the existence of 2 flavors of these Heads made such an error probable and may have been the reason to change the GTO Heads (rather than any failure problem that may have materialized in the first few months of production).

Wonder how many other early '64 421HOs got the XX Heads (and for that matter, I wonder if any early '64 GTOs got the XO Heads).

Had given up trying to discover what those stamped codes meant. Neat to finally get some compelling evidence.

W.E., new info?

716 differences
 

These show the part number difference. One setting on later pad vs. early no pad or platform.

Phoenix is usually warmer than this but it did warm up a couple nites ago at a friends shop. 4 sets of 716 heads appeared and I took the opportunity to get some pics and observe differences.
There is no left or right head as one casting can be used for either side. However it must have been interesting to see the amount of 716 foundry patterns used during a pour.

The earliest, L32, is cast upside down,(compared to part number) and has X and O stamped at the button pads at the center exhaust ports. To the very end and right of the cast part number, is a small pad that has a line as shown with my pen in the picture.

The next pair J193, is cast upside down and has X and X with the end button pads having a line on one head and + on the other. I suppose one could say plus or minus.

E84 pair has the date upright and has X and O at center exhaust port. The end button pads are + and +.

E224 and E254 are different at the exhaust port. Dates cast upright. A fair amount of rust on 22 but looks like O and X. E254 has nothing in the first exhaust pad but looks like the O above two X`s on the second pad. Again there is a bit of rust but visable under a glass. The end button on 25 has the + and the 22 has the minus.

Not sure if this helps or what the end buttons tell us. Maybe day or nite but these are not stamped but cast in. Foundry number 1 is on all of the heads so it is likely only one line cast heads.

I was promised access to 5 different 1964 trips manifolds so that will be next week.

Interesting on the end pads.

:)

Ya'll need to get those pics more in focus.