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I just ordered a new set of reproduction 68-72 crank and water pump pulleys for my 454 car, and a corresponding reproduction 3940992 power steering belt, as well as a 3952336 water pump belt.
The vendor is a well known vendor.
The 3952336 belt is a Quanta belt, and appears to be robust in quality It fits appropriately in the groove on the crank pulley. The 3940992 belt came in a plain white slip package, and appears quite thin...it easily falls into the crank pulley groove and bottoms out on its belly.
There is just no way that the 3940992 can possibly operate correctly. Im not looking for originality in appearance, Im looking for function...I don't want to hear this damn thing squeal anymore and am trying everything possible to eliminate it. New pulleys, captured water pump belt, idler pulley for that belt, etc..Im done with this nonsense and don't want this belt to stand in my way.
Long story short, does anyone have any experience with the 3940992 belt? Does it appear to be too thin? Was it in Quanta packaging etc?
There is just no way that the 3940992 can possibly operate correctly. Im not looking for originality in appearance, Im looking for function...I don't want to hear this damn thing squeal anymore and am trying everything possible to eliminate it. New pulleys, captured water pump belt, idler pulley for that belt, etc..Im done with this nonsense and don't want this belt to stand in my way.
Long story short, does anyone have any experience with the 3940992 belt? Does it appear to be too thin? Was it in Quanta packaging etc?
I am not seeing where the 3940992 is applicable to a BB Corvette. Quanta/Gastanks. com doesn't list it for '74 (from your profile).
Here's the GM Corvette parts book page for '74 belts:
I am not seeing where the 3940992 is applicable to a BB Corvette. Quanta/Gastanks. com doesn't list it for '74 (from your profile).
Here's the GM Corvette parts book page for '74 belts:
Ignore the fact that the body is a 1974. I have purchased 68-72 Pulleys for the car. The pulleys are not correct for a 74 454 with A/C, however to replace my original pulleys with correct 1974 pulleys is impossible. In an attempt to replace all components so that I no longer get belt squeal, this was the only way I could replace my pulleys. The belt I have selected is for a 68-72.
Ignore the fact that the body is a 1974. I have purchased 68-72 Pulleys for the car. The pulleys are not correct for a 74 454 with A/C, however to replace my original pulleys with correct 1974 pulleys is impossible. In an attempt to replace all components so that I no longer get belt squeal, this was the only way I could replace my pulleys. The belt I have selected is for a 68-72.
Visit the GM parts link I posted above and go back a couple pages. You still won't find that 3940992 belt. I found one reference to '69 Corvette using it for P/S (43.5") but not in the Corvette-only parts books. The 992 belt was used for other GM products.
I am not seeing where the 3940992 is applicable to a BB Corvette. Quanta/Gastanks. com doesn't list it for '74 (from your profile).
Here's the GM Corvette parts book page for '74 belts:
Originally Posted by 67:72
Visit the GM parts link I posted above and go back a couple pages. You still won't find that 3940992 belt. I found one reference to '69 Corvette using it for P/S (43.5") but not in the Corvette-only parts books. The 992 belt was used for other GM products.
Ahhh. It's not listed in the parts books, but that number was used in the assembly manual; must not have been available under that # as a service replacement. Is the width of your Quanta belt 7/16"?
Unless you are after the debossed part # on the belt's face for originality, perhaps take the belt to NAPA to see if they can find a variation of the same length but wider. Perhaps an A or B section belt.
I have accumulated some of this info as well, and bought many of the pulleys.
I hope the right ones. I have not figured out my belts yet.
There were close to a half-dozen different BB WP and Crankshaft pulleys over the years.
And yes the 74 ones were one year only.
Some of them a different diameter, by up to an inch, which changes the pulley ratios and the belt lengths.
These are from my 82 Parts Book. BB Crankshaft Pulleys & Applications
BB WP Pulleys by Application
Fortunately the BB PS pulley stayed the same, 3878245
The alternator pulley moved front or back to change the belt landing on the 1st or 2nd row, depending if PS or not.
I have the belt charts as well, and they vary by year, but they are pretty useless until you know exactly what pulley combination you have, and if it exactly matches a stock optioned setup. with: PS, AC, AIR pump etc.
69 BB Drive Belt Chart
70 BB Drive Belt Chart
71-72 Drive Belt Chart
71-72 AIR Belt
This stuff really needs to be combined into one big selection chart LOL!
Last edited by leigh1322; Sep 7, 2024 at 12:08 PM.
If your belt is bottoming out in the groove, it's definately too narrow. Or the groove is too wide.
As mfgrs consolidate old part numbers, often the substitute is only close, and just does not fit/function as well.
Which crank pulley?
The normal steel BB crank 3921923 pulley has 2 grooves and is 6-3/4" wide. The belt sits flush with the top.
The high performance cast iron BB crank pulley 3863108 has 2 grooves, is 6-3/4" wide, but has deeper belt grooves. The belt sits a couple mm inside the top edge.
GM says the 9433738 is the right belt for all BB PS up to 73. It should be 7/16" wide at the top and 43.25" long circumference. Measure the depth also.
Measure your current belt specs against that.
The 74 PS belts are slightly wider and/or 1/2" longer on the 74 to accomodate the larger crank pulley.
I have one of each of those two crank pulleys here, if it becomes necessary to measure the groove depth. My steel one is GM OE.
That would help you determine if the repop pulley is not made correctly, This stuff happens.
Or it could be as simple as you have a deep cut belt and shallow cut pulleys.
Last edited by leigh1322; Sep 7, 2024 at 02:01 PM.
If your belt is bottoming out in the groove, it's definately too narrow. Or the groove is too wide.
As mfgrs consolidate old part numbers, often the substitute is only close, and just does not fit/function as well.
Which crank pulley?
The normal steel BB crank 3921923 pulley has 2 grooves and is 6-3/4" wide. The belt sits flush with the top.
The high performance cast iron BB crank pulley 3863108 has 2 grooves, is 6-3/4" wide, but has deeper belt grooves. The belt sits a couple mm inside the top edge.
GM says the 9433738 is the right belt for all BB PS up to 73. It should be 7/16" wide at the top and 43.25" long circumference. Measure the depth also.
Measure your current belt specs against that.
The 74 PS belts are slightly wider and/or 1/2" longer on the 74 to accomodate the larger crank pulley.
I have one of each of those two crank pulleys here, if it becomes necessary to measure the groove depth. My steel one is GM OE.
That would help you determine if the repop pulley is not made correctly, This stuff happens.
Or it could be as simple as you have a deep cut belt and shallow cut pulleys.
Thank you for the effort and info.
The crank pulley is a repop 3921923. It has a GM stamp on it, but I guess that's part of the whole reproduction.
As you stated, it measures 6 3/4".
The 3952336 reproduction quanta belt fits perfectly in the grooves, and is level at the top of the grooves. It measures 7/16" across the top.
The 3940992 belt is what all the corvette vendors [corvette central, zip, mid America etc] are selling as a "correct" belt for 454 cars. I find it interesting that there is contradictory literature. It measures 3/8" across the top, and came in a white unmarked sleeve, leaving me to believe it is not a quanta belt.
Originality is not important here.. just function.
With my previous 74 pulleys, I used to run a green stripe 9440 belt. Chances are Im going to pursue that series, and return this belt to the vendor.
It probably used to be 7/16 and then the belt mfgr thought 3/8 was close enough. Call Quanta. They will want to know it's off spec. So they can correct it.
Another 454 belt thread
