I have an early 1967 GT350 equipped with factory A/C and the associated re-stamped C7ZE A harmonic balancer. I came across a nearly seven year old forum thread today that clarified the origin of the aforementioned part.
My engine is in need of a new timing chain and gears and is currently equipped with the wider non-HiPo chain (ca. 3/4in.) and timing gears and there is no counterweight present behind the C7ZE balancer. I believe these parts to be original to the engine, but cannot be absolutely certain.
It would assist me greatly if a more experienced source could elaborate on an early 1967 A/C-equipped GT350's timing chain and gears configuration, so that I might attempt to verify that my current configuration is indeed original. This being the case, perhaps the "hatchet" counterweight was omitted on this engine for some reason and an alternative flywheel was installed to compensate for the differing mass?
Alternatively, possibly the gears and chain were replaced previously with the wider non-K-code parts and the counterweight was removed due to interference issues. However, this seems equally unlikely. Any light that you can shed on this matter would be greatly appreciated indeed.
Quote from: localzero on April 08, 2026, 07:53:52 PM. . . . . perhaps the "hatchet" counterweight was omitted on this engine for some reason and an alternative flywheel was installed to compensate for the differing mass?
Alternatively, possibly the gears and chain were replaced previously with the wider non-K-code parts and the counterweight was removed due to interference issues?
And it is the "unknowns" and "what-if's" that at this point probably dictate that your best option is to "assume" that those whom proceeded you at least had an inkling of a notion of what they were doing and now you will follow their lead. Any ideals of wanting "absolute" conclusions would dictate that the revolving and reciprocating assembly be (re)balanced. ;)
Also, always check the gear to gear alignment, ensuring that there isn't any offset. :)
Scott.
Are you sure that is the original Engine?
Have you contacted Dave Mathews the SAAC '67 Registrar? He might know/have some history on your car that could help.
'67 Shelby Registrar - Dave Mathews: 67registrar@saac.com
Hi to all,
First question is did it run smooth? If so it must have been balanced without the hatchet.Not a big deal but it does mean someone has been inside this engine. On the positive side you can now use the
Timing chain of your choice.No clearance problems. The hatchet with a narrow chain is getting to be expensive and seems like someone has already made this choice for you. Unless you are planning a total rebalance, it may be best to replace and get running again with new parts. Also the difference with A/C is in the step to allow a pulley to mount-no balance difference.The other question is why do you consider it an early car?
R.R.
Hello Scott,
Many thanks for the input. This is likely sage advice and was my initial inclination as well. However, other than a replacement Accel dual-point distributor, the car was essentially in the same state that it left Shelby American when I purchased it in 1987..albeit a lot worse for wear.
The misnomer here remains the over-stamped C7ZE balancer and I'm holding out hope that another forum participant might have knowledge of just how these early 1967 GT350s were modified to accommodate the air-conditioning system. Barring any additional commentary, I'll likely replace the chain and gears with like components as suggested. Regardless, I cannot recall that the engine seemed out of balance when I last drove the car. It vibration presents thereafter, I'll have to reconsider adding the aforementioned "hatchet" counterweight and the compatible narrower gears and chain subsequent. Not a quick job, but manageable.
Regards,
Tom
Quote from: localzero on April 08, 2026, 07:53:52 PMI have an early 1967 GT350 equipped with factory A/C and the associated re-stamped C7ZE A harmonic balancer. I came across a nearly seven year old forum thread today that clarified the origin of the aforementioned part.
My engine is in need of a new timing chain and gears and is currently equipped with the wider non-HiPo chain (ca. 3/4in.) and timing gears and there is no counterweight present behind the C7ZE balancer. I believe these parts to be original to the engine, but cannot be absolutely certain.
It would assist me greatly if a more experienced source could elaborate on an early 1967 A/C-equipped GT350's timing chain and gears configuration, so that I might attempt to verify that my current configuration is indeed original. This being the case, perhaps the "hatchet" counterweight was omitted on this engine for some reason and an alternative flywheel was installed to compensate for the differing mass?
Alternatively, possibly the gears and chain were replaced previously with the wider non-K-code parts and the counterweight was removed due to interference issues. However, this seems equally unlikely. Any light that you can shed on this matter would be greatly appreciated indeed.
Would you please elaborate on your understanding of the "associated re-stamped C7ZE A harmonic balancer" and how it relates to the early 67 GT350 engine.
+1
Quote from: JD on April 09, 2026, 08:46:59 AMHave you contacted Dave Mathews the SAAC '67 Registrar? He might know/have some history on your car that could help.
'67 Shelby Registrar - Dave Mathews: 67registrar@saac.com
Ask if any warranty work is shown.
Greetings all,
Firstly, many thanks to all for your engagement on this. Next, the block is indeed original to the car. As mentioned above, given the rare nature of this particular balancer and the condition of the OEM chain and gears, I tend to think that they are original as well. That being said, the wide chain anomaly calls this into question.
Next, to the best of my recollection, this example is not currently in the registry. Nonetheless, I intend to rectify this soon. However, I have owned it since 1987 and it's simply languished as I worked on other projects, Shelby and otherwise. During this time, it was rarely driven and, as pointed out, as best I can remember, there was no excessive vibration present. Regardless, suggesting that I contact Dave Matthews is excellent advice and I will most certainly do so.
Regarding Bob's question about the modified over-stamped C7ZE balancer, it was my understanding that this was an early "quick fix" designed to accommodate the three row pulley required for A/C and perhaps an air pump in CA. Subsequent, a different balancer with similar dimensions was introduced with a C8ZE part number. I'd be curious to know when this occurred. Furthermore, it has occurred to me that perhaps as part of the C7ZE fix, the counterweight was eliminated and the flywheel rebalanced to compensate. A crazy idea to be sure, but maybe possible?
Furthermore, I consider my 350 to be reasonably "early", as its production number is around 1200. It's an inboard light car and appears to be consistent with this production period. I have absolutely no idea how many A/C-equipped 350s were constructed prior, but I imagine that it wasn't many, given the over-stamped balancer fix that was implemented to accommodate this somewhat rare option.
Additionally, it's definitely a possibility that the engine has been apart and at some point rebalanced without the counterweight in situ, sometime prior to my ownership. I simply don't see any evidence of this and the wear on the FoMoCo timimg set seems to indicate otherwise.
Lastly, I was simply hoping that someone with another '67 350 with A/C, from my production range, could confirm
that their car has the counterweight present. If so, I have to conclude that the engine has been apart and presumably rebalanced during the process.
Once again, my sincerest appreciation to all that have contributed this far. I'm simply astounded by this level of assistance and am grateful for your expertise.
Regards,
Tom
Quote from: localzero on April 08, 2026, 07:53:52 PMI have an early 1967 GT350 equipped with factory A/C and the associated re-stamped C7ZE A harmonic balancer.
It would assist me greatly if a more experienced source could elaborate on an early 1967 A/C-equipped GT350's timing chain and gears configuration,
Quote from: localzero on April 09, 2026, 10:25:10 AMThe misnomer here remains the over-stamped C7ZE balancer and I'm holding out hope that another forum participant might have knowledge of just how these early 1967 GT350s were modified to accommodate the air-conditioning system.
If you're perhaps under the impression or just exploring whether these components may have been of a different makeup for A.C. cars vs. non, this would not have been the case. Yes, dampers were sometimes unique to a particular chassis or sometimes due to different belt-driven accessory componentry, this to provide for better fitments and/or in an understanding that those items being driven via the belt(s) do also participate in "damping", but not "balance" value items and hence here the change of unique timing chain & gearing. :)
As is often stated: "the "cookie-cutter" counter counter-weight was added for improved high R.P.M. balance", . . . . . this is not accurate. The actual reason was simply that the "289 Hi-Po" had different connecting rods & pistons which weighed more; and as attached to the same crankshaft casting (yes, "selected for higher nodularity") which was engineered and intended for something less, there needed to be an additional value added somewhere, and the "cookie-cutter" installation was deemed the most expedient solution. And this would not have been deletable just because A.C. was added. ;)
Scott.
Quote from: pbf777 on April 09, 2026, 11:32:19 AMQuote from: localzero on April 08, 2026, 07:53:52 PMI have an early 1967 GT350 equipped with factory A/C and the associated re-stamped C7ZE A harmonic balancer.
It would assist me greatly if a more experienced source could elaborate on an early 1967 A/C-equipped GT350's timing chain and gears configuration,
Quote from: localzero on April 09, 2026, 10:25:10 AMThe misnomer here remains the over-stamped C7ZE balancer and I'm holding out hope that another forum participant might have knowledge of just how these early 1967 GT350s were modified to accommodate the air-conditioning system.
If you're perhaps under the impression or just exploring whether these components may have been of a different makeup for A.C. cars vs. non, this would not have been the case. Yes, dampers were sometimes unique to a particular chassis or sometimes due to different belt-driven accessory componentry, this to provide for better fitments and/or in an understanding that those items being driven via the belt(s) do also participate in "damping", but not "balance" value items and hence here the change of unique timing chain & gearing. :)
As is often stated: "the "cookie-cutter" counter counter-weight was added for improved high R.P.M. balance", . . . . . this is not accurate. The actual reason was simply that the "289 Hi-Po" had different connecting rods & pistons which weighed more; and as attached to the same crankshaft casting (yes, "selected for higher nodularity") which was engineered and intended for something less, there needed to be an additional value added somewhere, and the "cookie-cutter" installation was deemed the most expedient solution. And this would not have been deletable just because A.C. was added. ;)
Scott.
All of this is indeed more or less correct. However, the fact remains that the C7ZE balancer was relieved of material to allow it mount closer the block to provide clearance for the 3-row pulley for the A/C compressor and/or CA air pump drive. This makes this balancer unique to A/C-equipped '67 350s. The same applies to the associated 3-row crank pulley. This isn't really conjecture, it's simply fact.
My way of thinking is that this did indeed alter the mass of the balancer relative to the non-A/C C5OE A balancer that it was machined down from, albeit if only very little. Given the the counterweight clearance was minimal to begin with, this likely drove the decision to incorporate the obviously less robust narrower timing chain and gears on all K-code engines. On a related note, the narrower chain and crank gear also likely weigh less than the wider standard OEM 289 parts. This probably accounts, in part, for the more massive C5OE balancer on the K-code engines.
As you've correctly pointed out, the counterweight was installed to compensate for the off-center mass of the larger 3/8" rod bolts. Perhaps since all of the modified parts that were required to fit A/C were mounted on the center line, the additional mass wasn't deemed to be a rotational issue. That said, I seem to recall that later SBFs equipped with 50oz balancers in place of the 28oz. variety used a different flywheel accordingly.
All I'm saying here is that the notion that the rotational mass was in balance is likely correct in both A/C and non-A/C-equipped cases. However, the total mass of the rotational assemblies was obviously not the same. This starts to look suspicious on the A/C-equipped engines when one considers all of the variables of additional mass mounted on the center line: 3-row pulley, machined C7ZE balancer and the "hatchet' counterweight or not. I'm making a lot of assumptions here, but I suspect that the Ford engineers were well aware of all of this in 1967 when the cobbled together the C7ZE fix. I simply hoping that somewhere in the brain trust this knowledge still exists. Thanks again for the valuable input and insights.
On a final note, it's worth mentioning that it simply didn't occur to me that Dave might have access to vintage service record detail and my next effort will be to compose an email posing this question and other related ones. If this is indeed the case, I can only wonder why the delivering dealership seems to struggle to locate the service history related to the airbag recall on my '07 GT500, but go figure?
Regards,
Tom
The "damper" was machined to clear the three sheave pulley to align with the proper accessories. It would have no bearing on the relationship to the stock K rotating assembly. The factory (Ford) IMHO would not build a number of K 289 engines to accommodate the limited number of K equipped cars that had the air conditioning option.
It was cheaper to machine a K "damper" than to remove the timing cover and swap the timing components.
(edited for vocabulary and clarity)
Joe
The inner circumference on the balancer outer ring was machined to accept the wider 3-sheave pulley, but the imbalance remained the same. Looking at the back side of the balancer, you will see that the imbalance weighting of the hub part of the balancer is unchanged. Only the outer ring on outside of the elastomer was machined = no change in the balance. There would be no reason to change any balancing or removing of hatchet to accommodate for AC.
I suspect hatchet was removed to allow for wider timing chain, probably accompanied by a rebalance.
Quote from: 67350#1242 on April 09, 2026, 01:32:04 PMThe inner circumference on the balancer outer ring was machined to accept the wider 3-sheave pulley, but the imbalance remained the same. Looking at the back side of the balancer, you will see that the imbalance weighting of the hub part of the balancer is unchanged. Only the outer ring on outside of the elastomer was machined = no change in the balance. There would be no reason to change any balancing or removing of hatchet to accommodate for AC.
I suspect hatchet was removed to allow for wider timing chain, probably accompanied by a rebalance.
+1 :)
Quote from: localzero on April 09, 2026, 12:45:01 PMThe fact remains that the C7ZE balancer was relieved of material to allow it mount closer the block to provide clearance for the 3-row pulley for the A/C compressor and/or CA air pump drive. This makes this balancer unique to A/C-equipped '67 350s. The same applies to the associated 3-row crank pulley. This isn't really conjecture, it's simply fact.
My way of thinking is that this did indeed alter the mass of the balancer relative to the non-A/C C5OE A balancer that it was machined down from, albeit if only very little. Given the the counterweight clearance was minimal to begin with, this likely drove the decision to incorporate the obviously less robust narrower timing chain and gears on all K-code engines. On a related note, the narrower chain and crank gear also likely weigh less than the wider standard OEM 289 parts. This probably accounts, in part, for the more massive C5OE balancer on the K-code engines.
All I'm saying here is that the notion that the rotational mass was in balance is likely correct in both A/C and non-A/C-equipped cases. However, the total mass of the rotational assemblies was obviously not the same. This starts to look suspicious on the A/C-equipped engines when one considers all of the variables of additional mass mounted on the center line: 3-row pulley, machined C7ZE balancer and the "hatchet' counterweight or not.
Not to be stickler for details, but first lets' rectify the vocabulary that might be a participant in the confusion, that of "balancer". There's no such thing! At least not as properly applicable terminology in this discussion. It is properly identified as a "harmonic/vibration damper" or simply a "damper"; though some damper assemblies "may" consist of a counter-balance feature (as is the case here) and it is this that has led to the moniker of "balancer" or even "harmonic balancer", etc., both of which are really not a good choice. :)
Now, "changing the mass of the balancer", not specifically any counter-weight feature, doesn't really change the "balance", nor does that as effected by adding or subtracting other features such as pulleys or T.C. gears, this as long as they themselves don't inject an unintended imbalance; though these may change the frequency of the "critical" vibratory feature within the mass of the whole assembly. This meaning that to narrow or reduce the diameter of the inertia ring or to open-up the internal dimension of the hub, symmetrically, isn't going to greatly effect the balance requiring a correction such as the addition or removal of the "cookie-cutter" weight. ;)
Next, the reason for the requirement of the narrower chain & gear when the additional counter weight was added on the H.P. engines was because the stacking length of componentry as mounted on the nose of the crankshaft had to remain the same under the retaining bolt head; so with the .150" added in with the counter weight, this sum had to come-off somewhere else.
So, did the "damper" assembly actually get moved rearward, "closer to the block"? If this had been deemed a reasonable possibility there wouldn't have been a need for the narrower chain & gear concoction, just turn .150" off the damper snout and we're done! Or is it that the timing cover and water pump changed and got closer to the damper and this coupled with just choosing to adopt the specified larger inertia ring damper ("dampening" value), and this for expediency just being barrowed from the earlier 289 H.P. engineering, which being wider, brought it into an interference scenario and which was most expediently solved by machining the damper inertia ring "some" to fit, as the engineers understood that it wouldn't greatly effect the "balance"? :-\
Or maybe something like that? ::)
Scott.
Hi Again,
Just to get a point across. The C7 restamped harmonic balancer was only stepped to allow for pulley
Offset-this does not affect balance or change the distance/clearances involved with the hatchet.
Much like machining a flywheel when replacing a clutch,will not require a rebalance. I have chased 67 A/C K cars for over 40 years and have learned a lot of mis-understandings/rumors Facts are
They are rare, as the total was 132 cars. Most books say A/C was not available with a K engine.....
This is because most people have not seen one. Ford/Shelby first equipped cars with A/C in 1966 when they finished the year with 4 Convertibles.We have documents showing the special request for K engines with A/C. For 1967 Ford used the same setup for the crank pulley and it was given a new part number to show the change.The C8 part is different and became a common replacement.A K engine will have EXTREME imbalance if the hatchet is removed and the engine is not rebalanced. It is actually 30.2 ounces with a K engine because of the hatchet,heaver rods and different flywheel/harmonic balancer ....A standard 289 is 28 ounces.The best way to check out your engine is remove the oil pan and inspect/verify what you find. And a car built in the 1200 range is not considered "Early" to be precise it would have to be in the first few hundred and finished by Shelby before Jan 1967.
Hope this clears up any rumors/myths that you may have. Jim Cowles (r.i.p.)is the only other person that seemed to understand K cars with A/C and we really miss him.
R.R.
There are plenty of excellent insights above and tend to agree with all of them. Given that, to the best of my recollection, the engine didn't seem to present any abnormal vibration before the removal of the drive belts, crank pulley and timing cover, etc., I'm inclined to go with 67350#1242's assessment.
I've now also concluded that the hatchet counterweight was removed to accommodate the wider chain and am reasonably confident that the engine was rebalanced thereafter. Quite possibly this was the result of excessive wear to the original narrow chain and gears and the wider set may have seemed like the logical choice at the time. An interesting side-note: it's entirely possible that 67350#1242's A/C-equipped car was the example assembled right before mine.
I've ordered a new wider chain and gears timing set and will reassemble the front of the engine in the next week or two. Thereafter, the proof will be in the running, so to speak. I'll make it a point to update the thread regarding the outcome.
On a related note, I genuinely appreciate the input of every participant thus far and I'm grateful for your having pointed me in the right direction in this situation.
Tom
I may be too late, but I might suggest getting a roller type chain as long as you are in there?
I also own a 67 C code coupe with AC, and the only differences I see between it and the Shelby other than the damper modification, is the lack of A/C compressor brace between compressor and intake manifold, and the routing of the heater hoses, as the Shelby does not have a thermostatic choke - the one hose doesn't run through a clip on choke housing. The dampers used on C and A code engines did not have the wide outer ring and the wider A/C pully fits no problem. There is no boss on the cobra intake to mount the compressor brace and apparently it isn't needed.
I have also seen two differing 3-sheave A/C pulleys on these cars; one with larger and one with smaller diameter A/C pulleys. (the most forward sheave ) I believe the smaller diameter was used on the hipos to slow the compressor speed, but I have also seen them on non K code setups, maybe some sort of power option? If anyone has more info on this I would be curious to learn.
Thanks to R.R. for clarifying some of the details related to the hardware associated with the installation of A/C on the K engines. To be honest, I was unaware that the four '66 convertibles were so equipped. I was under the mistaken impression that this combination first occurred for the '67 model year. Furthermore, I wasn't certain that the A/C option was even available from the outset of production.
The over-stamped number on my harmonic dampener or balancer also contributed to the confusion and left me under the impression that this part and the associated pulley were part of a rather hastily implemented A/C fix. It obviously didn't affect the overall balance of the K engine, but did serve to alter slightly the weight of the rotating assembly and this concerned me.
Additionally, I've learned that the term "early" applies specifically to the cars assembled prior to January 1967. I used the term casually, as my example falls roughly into the first third of the production run for the '67 model year and this was indeed an error on my part.
67350#1242's subsequent suggestion of substituting a roller chain hadn't occurred to me actually, but this is an excellent idea. My paradigm has always been to err on the side of originality and this is probably what got me into trouble initially regarding the missing counterweight. I'll give the roller chain option some serious consideration and will likely order one. In many respects, the OEM timing components ship has already sailed and the lesson has been learned.
Given that there were only 132 350s assembled in the A/C configuration for '67, it's understandable that there's a not a massive brain trust relative to their specifics. I suspect that I was very fortunate indeed that all of you took the time to educate me and broaden the knowledge base somewhat in the process.
Tom