[dbnhs]

I'm helping a buddy rebuild the engine in his 64 GTO. The car has power
steering. We noticed that the two pulley's on the water pump are not the
same diameter, the inner one is about an inch smaller and has the holes
slotted in order to fit, as if it came off some other brand of engine.

My question: Are both pulley's suppose to be the same diameter on 64
engines? Thanks in advance.

[BOB VIDAN]

Sounds like the correct pulley if you have AC.

[Andre]

Instead of starting a new topic, I thought I would place the question in here as it seems to be the most pertinent of the prior posts to reference. I know 2006 was a long time ago.

Anyways fast forward to 2014. Helping a fellow board member with a water pump pulley for his 64 GTO with AC. I had what I believed is the correct one and shipped to him. It is a single stamped pulley with the front groove being a smaller diameter than the rear one. He agrees this configuration is correct, but that the front groove should be a 1/2" belt, and references a part number that indicates a 1/2" belt.

Did they measure the belts differently back in the day? I can't recollect ever seeing a pulley with different sized grooves, but I have limited experience in these cars compared to many.

Here is a picture of the pulley I sent him. The other pulley pictured is identical to the one that is on my car.

Any ideas or thoughts out there?

[John V.]

Andre, 9788886 is definitely not a '64 pulley. It was first used in '67 I believe.

The '64 pulley for A/C was p/n 544594.

It was first used in '63 for the Tempest w/ A/C.

I can't tell you the groove widths but I think you would have difficulty determining the expected groove width from the specified belt width.

The belts specified with this pulley were 1/2" for the front A/C drive and 13/32" for the rear alternator drive, except with PS which used a 3/8" belt to drive the alternator and PS pump from a common belt.

13/32" belt is only 1/32" wider than a 3/8" width belt, that seems pretty insignificant.

But it is not obvious to me why they specified a wider belt for the non-PS application vs. the PS application.

Looking at the belt depths for the specified belts for A/C application, they are all 5/16" depth except for the '63 version of the 1/2" wide belt, it shows 17/32" depth (p/n 534311) while the '64 version of this belt shows 5/16" depth (p/n 9772317 which might also have been a running change p/n for '63). A wider belt would ride higher in the groove than a narrower belt, all else being equal. I'm not sure what to make of the 17/32" depth, seems that would have rode quite high. Maybe that explains the p/n change.

The pulley should be 7-13/32" dia for the front groove, I believe the rear groove should be 8" dia.

In my experience with non-A/C water pump pulleys, the '64 pulleys will not have a p/n stamp on them. Starting in '65 they will.

If the pulley has no p/n on it and it has the correct pulley dias., unless he knows for sure that the groove widths DO differ, this could be a correct pulley.

I don't know about other brands, but weren't too many Pontiac water pump pulley applications with the two different dia. grooves and the '63/'64 544594 may be the only one lacking a p/n stamp.

[Andre]

Thanks John V.
I'm not sure why I labeled the 9788886 as 64. I used PY to look up all the numbers of pulleys that I had lying around. The pulley that I had that I believed was for '64 did not have a number stamped on it, and hence no writing on it by me with a junkyard pen. Since I don't have the pulley any more, I can't measure it, but I might have another one to make a measurement of the diameter.

I'm a bit stumped by the reference materials indicating a 1/2" belt for the front pulley. That is a significant piece of rubber. To my knowledge no ac belts of future production were as robust as that.

But lets say it was 1/2" then that means the drive pulley on the crank would have to be 1/2" also?

I know that there are belts that are coded for different depth pulleys, and using the wrong one causes squealing. Hoping someone with an original 64 ac car can chime in as to what they have. My car was put together from a junkyard fugitive, so while the system functions, it may not be correct.

[John V.]

Andre, according to the Resto Guide, all A/C drive belts were 1/2" thru '69, '70 shows 15/32".

I don't know about the crank pulley.

I believe I have a '64 crank pulley for A/C (also has the 2 different dia grooves). If I was sure where it is stored, I'd think about digging it out to check the groove widths.

Same balancer used for A/C on big cars, you might want to ask in the big car forum for somebody to check the groove widths for the A/C balancer pulley.

Still wouldn't prove the groove widths of the water pump pulley, but if they are same widths on the balancer pulley, that would be compelling evidence to suggest they could be same width on water pump pulley too.

Heck, what am I thinking? The '64 big Pontiac also used the same water pump pulley as the V8 Tempest. Surely somebody on the big Pontiac forum has an original A/C water pump pulley to check the groove widths.

Also, as I think about it, I believe it is the LARGER of the 2 water pump pulley grooves that was 7-13/32" dia, the front groove would be smaller dia.

[War eagle]

John the A/C compressor pulley is the tell-tale here as 63-66 appear to be the same 1/2" groove. The only exception is the T-4 with A/C which uses the 3/8 drive. The illustration in the MPC and Shop manual indicates the route of the belt and it includes the double groove water pump pulley, which is turned by the double two different groove crank pulley, and then the single 1/2inch compressor pulley. And you are correct. T-8 and P-8share these 2 different sized double groove pulleys. The chart in the MPC for Tempest and Pontiac belt drives makes it easy to tell what goes where.

[John V.]

W.E., understood. No question about which drive belt goes to which groove.

The question is whether the pulley grooves themselves are different widths.

The belt widths are definitely different, A/C being the 1/2" width.

Andre sold a pulley that apparently has same width grooves. The customer believes the front groove should be wider than the rear groove, since it turns the 1/2" wide belt.

If the '64 A/C water pump pulley should have 2 different width grooves, then apparently the one Andre sold is incorrect. I am not sure. Just because the belt widths differ, not sure that means the pulley groove widths differed.

From what I can tell, Pontiac did not have too many 2 groove water pump pulley applications where the front groove dia. was smaller than the rear groove dia. and from what I can tell, they all used a 1/2" wide front belt and a smaller width rear belt. If Andre's pulley has 2 same width grooves, it isn't clear what it might have come off of if the Pontiac pulleys did have 2 different width grooves.

Do you have a '64 A/C water pump pulley to check? I guess what Andre needs to know are the groove width measurements to compare with the one he sold.

[War eagle]

The rear most water pump groove drives the alternator and power steering pump which of course uses a 3/8 belt. The crank pulley also has the rear 3/8 width groove that drives the water pump. I have a pulley coming on lone and it matches the groove widths as noted. I have also seen a 64 Bonney (prior pics of a steel fan) that has the 2 different widths.
John the 3/8 belt groove of Andre`s will NOT allow the 1/2 inch belt to drop in and rides at least half way out of the groove.

[John V.]

W.E., makes sense to me.

Doing the math, a 36 deg belt, 1/2" belt width, with a 5/16" depth would ride just a hair more than 3/16" out of a 3/8" wide groove.

Perhaps this explains the specification for the 1/2"x62" belt p/n 534311 listed for '63 A/C use.

This belt has a depth of 17/32".

It would also ride more than 3/16" out of a 3/8" wide groove but would still have 11/32" of depth in the groove.

So now I'm wondering.

The diagrams in the MPC suggest the belt originally specified for the '63 T8 with A/C was the very deep p/n 534511.

The parts listing in Gr. 1.062 suggests there was a running change, as the shallower belt p/n 9772317 is listed for the '63 application.

If they ran the deeper belt in a 1/2" wide groove, I'm not sure the groove itself would have been deep enough.

I don't know how that would have affected the belt and the belt tension.

But maybe they realized it wasn't working properly, so they switched to the shallower p/n 9772317 belt.

I don't find any evidence in my '66 MPC of a concurrent change to the '63 pulley.

Going to the shallower belt would surely have required the front groove to be 1/2" width as W.E. points out, a 3/8" wide groove wouldn't allow this 1/2" wide belt to drop into the groove much at all.

Only thing I can think of is perhaps there was also an original '63 W.P. pulley where the grooves were both 3/8" wide and was used with the deep 1/2" wide belt.

Would have worked with the deep 1/2" wide belt albeit with a lot of belt riding out of the groove which might have caused unusual belt wear. But plenty of belt down in the groove.

Then maybe the change was to switch to the shallow 1/2" wide belt and also change the pulley so that the front groove was now 1/2".

Surely that would have meant a pulley p/n change. Since I have no evidence of a pulley p/n change, I'm not sure about this theory.

But it would at least explain the existence of Andre's pulley if there actually was an early design '63 Tempest with A/C water pump pulley with two 3/8" width grooves.

Since there are no p/ns stamped on the pulleys it is probably pointless to try to figure out the origin of Andre's pulley. But it seems to be a loose end to me, wish I could know the origin of it. Maybe a '63 Flash Bulletin or SCN would have addressed the belt change and could shed light on a possible pulley change also?

Andre, looks like the front groove for the correct '64 T8 with A/C pulley should have the 1/2" wide groove.

[pfilean]

Perhaps these picture will help if you can get them to print large enough to read. Notice that every time the picture shows a double size fan pulley that the crank pulley is also double size. I think that the 62 amp alt. always had a double belt .

[Andre]

All very confusing to me, and more so because there is no one chiming in with an original '64 a/c car (factory or field installed ac) that can add some evidence.
My '64 has a equal diameter pulley with equal grooves.
Looking front to back
Belt 1 loops crank, water pump and a/c compressor
Belt 2 loops crank, water pump, alternator and power steering.

It is exactly like the middle left diagram shown pfilean's post

[War eagle]

Andre. If you are looking at Pfilean middle left illustration, note that the A/C belt is numbered 12. Then go to the corresponding list he has posted next to it and look at 12. Doesn't that say 1/2 x 62??

[Andre]

Yeah, but I don't have a pulley with a groove wide enough for a 1/2" belt on my 64, so n I have been running a narrower belt that specified for 9 years. In addition the water pump pulley I have used doesn't have unequal diameters.

Seems like I remember a discussion on there regarding a different setup for 64 with A/C that used a whole mess of different parts. Maybe I just got lucky with my setup aligning and working as it should.

[John V.]

Andre, your equal diameter pulley is definitely wrong, I thought you already understood that.

The '64 water pump pulley is definitely consisting of two grooves with two DIFFERENT diameters.

Not only do I know this to be true, but you can confirm it by the illustration.

Look at the middle left and the bottom right illustrations.

They represent the two A/C applications, with or without PS.

The same Water Pump pulley is provided for both, item 13 & 28 respectively, both require p/n 544594.

Compare how this pulley is illustrated with the illustration bottom left for the two groove pulley used for PS without A/C, item 22. This pulley has two equal diameter grooves.

It is illustrated with a single circle.

But the water pump pulley for the A/C application, because it has two different dia. grooves, is illustrated with TWO different dia. circles.

That follows standard engineering graphics convention.

The 1/2" wide belt for the A/C drive is circumstantial evidence to prove the front groove must be wider than the rear groove.

I initially thought that needed evidence to prove. But W.E. correctly points out that a 5/16" deep belt (the depth of the '64 A/C drive belt) would barely drop into a 3/8" groove. I confirmed that by calculation, TAN 18 deg=.3249=.0625/x, x=.1924", just more than 3/16". The belt angle is 36 deg. The calculation is determining the ht. of a trapezoid with parallel bases of 3/8" and 1/2" length. The 1/2" belt will only drop into the 3/8" wide groove to the point where the belt is 3/8" wide. That forms the bottom of the trapezoid. The top is the width of the 1/2" belt.

18 deg is half the belt angle, .0625 means 1/16" overhangs to the right, 1/16" overhangs to the left. The ht. works out to be 0.1924" which is a hair more than 3/16". The total belt ht. is only 5/16", so less than 1/8" is down in the pulley groove.

As I point out, the belt listed in the illustration for the '63 Tempest V8 is 17/32" depth. It would be 11/32" down in a 3/8" groove and this corresponds well with the 5/16" which seems to be the target depth.

That is why I suspect that they may have had a two groove pulley with both grooves 3/8" wide in '63. Putting a 17/32" deep 1/2" wide belt in a 1/2" wide groove likely wouldn't work because the groove isn't typically all that deep. Putting it in a 3/8" wide groove would be okay.

But the '64 specified the 1/2" wide, 5/16" deep belt. It had to run in a 1/2" wide groove, no way would 1/8" down in the groove be acceptable.

If you are running 3/8"wide belts, I'm curious about the balancer assembly you are using, is it the '64 A/C unit or something else? If the '64, a 3/8" wide A/C drive belt will be down in the groove. I don't think that is recommended, but not sure what harm it would do.

[War eagle]

I continue to investigate the water pump pulley as used on the 64, big/little cars with air, and with pretty good evidence, indicates the w/p pulley grooves are both 3/8inch. I believe the correct belt is a 3/8in wide unit. It occurred to me to run the 50 year old factory part number for the a/c belt 9772317 and see what comes up. The local O`Riellys crossed the number directly to their brand. The width and length confirm the 3/8 x 62 and NOT a 1/2 X 62 as indicated in the Pontiac parts book. I will be adding the compressor shortly and give the 3/8 belt a shot. I believe the a/c pump and crank grooves are 1/2in regardless. The net result should drop the belt deeper into the grooves and creates a DEEP GROOVE similar to hi-po pulleys designed to help eliminate belt throwing at high RPM. The water/pump of course would not get that deep groove so it continues to evade reasoning. 4 such big cars and my GTO all have the double groove 3/8water pump pulley (exactly like Andres 2nd example in post #3) and that evidence is compelling. The cross of the part number to 3/8 also supports an error in the Pontiac parts book.

[Andre]

I kind of thought the same thing, but I just didn't have the energy or inclination to argue what I have seen on cars in the field as opposed to the printed word. The guy I sold the pulley to insisted it was wrong wrong wrong so he sent it back. The printed material that was quoted seemed to back him up. He swore up and down it was from a 71 or later. Of all the Pontiac pulleys that I have seen and still own, this is the only one that I recollect being of this odd configuration.
Now granted I actually have more than one of these and I distinctly remember which cars I took each of them off of.
Others might remember in an earlier post I asked if they simply measured differently when indicating 1/2". Although I didn't state it, I wondered if that 1/2" had something to do with depth as opposed to actual width. I don't know if that makes any sense.

I figured by now that some other guys with '64 ac cars would chime in one way or the other as to whether it was 3/8" wide or 1/2" wide.

Again, I don't have anything to base my findings except of observations of actual parts, not books that tell of what might be as opposed to what really happened. My observations indicate 3/8" wide groove on the a/c compressor also. I offer the picture of my car. It is far from correct, and far from original and is a Fremont car, but you can clearly see that the belt fits perfectly and measures out as 3/8" and the groove is not close to 1/2". (from the 1" mark on the tape to 1 3/8") It should be noted that this is of course not the factory compressor, so maybe those had a 1/2" wide groove. This compressor does match the other 1/2 dozen that I have kicking around.

Now if someone comes along and shows me an actual 64 water pump pulley with 1/2" wide groove I will believe it.

[John V.]

W.E., I still lean to some other explanation.

As you know, my "unneeded" parts list says that I have a '64 544594 water pump pulley from a '64 GP with A/C. Have not found it yet, but believe it will likely show same groove dimensions as all the ones you've seen.

But I do not think a belt description error makes sense.

The A/C belts are generally ALL shown as 1/2" belts thru the '66 MY (and likely beyond) in the '66 MPC.

And this includes numerous belt p/ns issued both before and after 9772317.

It is illogical to me that the '64 would have been detailed with a 3/8" belt when all previous and subsequent applications show 1/2".

And if they are ALL described incorrectly, that also defies logic. Surely they did not keep making the same description mistake time after time.

I did find one bit of info in the Parts History.

When 9772317 was discontinued (I found it in a 1/82 dated History at PartsWiki), it shows to use 9433775.

This belt is 7/16"x61.5".

Belt p/n 9433929 was 1/2"x62". If 9772317 was 1/2", why GM did not recommend this one instead I can't explain.

I found another discontinued 1/2" width belt (9782706) first superseded by 9786985 and then 9786985 was discontinued and shown to use a 7/16" wide belt (9433758).

Andre's post got me to thinking. I'm sure the 1/2" indicated the width, not depth, but I turned to the '64 Tempest AMA specs to find this:

Belt H is the V8 A/C Drive Belt.

36 deg, that checks with the MPC.

62.0 nominal length (SAE), that checks with the MPC.

Width is shown as .47, not quite 1/2". Not sure what to make of that, but in the Belt Chart that shows the later model belt p/ns (ie., 9433775), the 7/16" belts are indicated as .440, the 1/2" belts as .500.

I don't know what to make of that except that perhaps GM preferred to substitute with a marginally narrower belt instead of a marginally wider belt.

Maybe there has been a v belt dimensional change since '64 such that a 1/2" wide belt became marginally wider than a 1/2" wide belt had been in '64.

I'm stretching here and not oblivious to the fact that the water pump groove may not be wide enough for a 1/2" width belt, whether .47 or .500 wide.

The AMA specs show the '64 6 cyl A/C belt dimensions as 55.5" long, .47 width, consistent with the dimensions in the MPC for p/n 9775899.

Also discontinued 1/82, it says to use 9433762, 55" long, 7/16" width.

[War eagle]

Andre there is a cast date on the very back of your A6 (opposite end from pulley). This will date your compressor BUT NOT the pulley/clutch. I believe you have a later compressor or pulley which DOES have a 3/8 groove.
Next measure the A/C belt groove on the crank. Of 4 original appearing 1964 cars with A/C, they all have a wide 1/2 groove and a smaller 3/8 groove.

I will run over at get some pics of a dated 64 compressor and show the 1/2in groove and crank pulley and post shortly.

[War eagle]

John I HOPE you find the pulley and unlike all of the others I have examined--has a stamped part number. I find no part numbers on 64 a/c w/p pulleys.
I doubt if a narrow 1/2 in belt existed(at least not intentionally) after all the 64 goat was not the first rodeo for that size belt.
I would be comfortable with a .4375 belt in both the 1/2 a/c groove and crank had the engineers designated it. The w/p acts more like an idler. But if GM wanted a 7/16 belt, than they would have called for it. And as for catalog errors continuing on into infinity, I can point out quite a few both in the Pontiac and Chevrolet mpc`s. (One chevelle item was leaf springs under the famous Z16 with a part number still listed in the 1971 MPC. They had coils)
I`ll get some pics shortly of original pulleys and post.