Water Pump Pulley for 74
Thread Starter
Instructor
Joined: Dec 2020
Posts: 126
Likes: 27
From: Mesa, AZ
Water Pump Pulley for 74
Does anyone know the difference between these two water pump pulleys for a 74? Both double groove and both for the small block. One is for an AC equipped car and the other isn't. Is the AC track a deeper groove?
https://www.zip-corvette.com/71-74-350-w-ac-water-pump-pulley.html
https://www.zip-corvette.com/71-80-water-pump-pulley-double-groove.html
https://www.zip-corvette.com/71-74-350-w-ac-water-pump-pulley.html
https://www.zip-corvette.com/71-80-water-pump-pulley-double-groove.html
Dr. Detroit
Joined: Mar 2012
Posts: 10,093
Likes: 4,017
From: New Braunfels Texas
I am not aware of any differences in Vette water pump pulleys from 71' on.......pre-71' had a 1/2 shaft rather than 5/8" so the hole is different.......but the pulleys themselves were the same.......there may have been subtle changes but nothing major.
I am pretty sure that the difference in those two pulleys is that one is new and one used.......
Jebby
I am pretty sure that the difference in those two pulleys is that one is new and one used.......
Jebby
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
IDK about deeper groove but maybe the difference is the bolt pattern to the W.P.
When I first got my Vette, my local parts store had a bling chrome W.P. pulley hanging on the wall. It would go well with my other bling parts.
Says: Fits All SBC from 1800's to 2023.
The bolts holes could not be farther off. Took it back, tried another. Same outcome. Gave up and now enjoy a black stock unit.
Somebody on tis forum mentioned the different bolt patterns on pulleys and that with a drill press they bore new holes.
H-m-m-m. Me thinks that's a bad idea if that is the issue.
When I first got my Vette, my local parts store had a bling chrome W.P. pulley hanging on the wall. It would go well with my other bling parts.
Says: Fits All SBC from 1800's to 2023.
The bolts holes could not be farther off. Took it back, tried another. Same outcome. Gave up and now enjoy a black stock unit.
Somebody on tis forum mentioned the different bolt patterns on pulleys and that with a drill press they bore new holes.
H-m-m-m. Me thinks that's a bad idea if that is the issue.
Le Mans Master
Joined: Jan 2001
Posts: 6,672
Likes: 1,363
Look at the corvette central webpage.
Pretty sure that M-3768 pulley at zip is this guy at corvette central:
https://www.corvettecentral.com/c3-6...ler-balance%2f
Look at your AIM. and you should be able to find the pulley number for your application. Corvette Central has the GM part number for this as GM Item No. 3991424
Pretty sure that M-3768 pulley at zip is this guy at corvette central:
https://www.corvettecentral.com/c3-6...ler-balance%2f
Look at your AIM. and you should be able to find the pulley number for your application. Corvette Central has the GM part number for this as GM Item No. 3991424
Race Director
Joined: Oct 2000
Posts: 12,624
Likes: 3,097
From: Shamong, NJ
My 83 Corvette Parts Book lists two water pump pulleys for the 74 small block.
3991423 was the water pump pulley for cars without AC, and is described as being a 2 groove pulley, 5 13/16" in diameter. This pulley was used on 71-77 350's without AC, and on all 78-80's with the L-82 350.
3991424 was the pump pulley for cars with air conditioning. I know it was two groove, but the Parts Book doesn't give the dimensions for this pulley, but from other information I have I believe it was 6 1/8" diameter. It was listed for use on 71-74 350's.
Because 74 L-82's came with A.I.R. they also used a second, single groove pulley on the water pump to drive the A.I.R. pump. This was an add on pulley that was used along with the two groove water pump pulley.
3991423 was the water pump pulley for cars without AC, and is described as being a 2 groove pulley, 5 13/16" in diameter. This pulley was used on 71-77 350's without AC, and on all 78-80's with the L-82 350.
3991424 was the pump pulley for cars with air conditioning. I know it was two groove, but the Parts Book doesn't give the dimensions for this pulley, but from other information I have I believe it was 6 1/8" diameter. It was listed for use on 71-74 350's.
Because 74 L-82's came with A.I.R. they also used a second, single groove pulley on the water pump to drive the A.I.R. pump. This was an add on pulley that was used along with the two groove water pump pulley.
Le Mans Master
Joined: Jan 2001
Posts: 6,672
Likes: 1,363
Per gmpartswiki 3991423 is 5 13/16" ..... http://www.gmpartswiki.com/getpage?pageid=40143
This website, Volunteer Vette, states that 3991424 is a 6" diameter pulley. https://www.volvette.com/EN60N.html
This website, Volunteer Vette, states that 3991424 is a 6" diameter pulley. https://www.volvette.com/EN60N.html
My 83 Corvette Parts Book lists two water pump pulleys for the 74 small block.
3991423 was the water pump pulley for cars without AC, and is described as being a 2 groove pulley, 5 13/16" in diameter. This pulley was used on 71-77 350's without AC, and on all 78-80's with the L-82 350.
3991424 was the pump pulley for cars with air conditioning. I know it was two groove, but the Parts Book doesn't give the dimensions for this pulley, but from other information I have I believe it was 6 1/8" diameter. It was listed for use on 71-74 350's.
Because 74 L-82's came with A.I.R. they also used a second, single groove pulley on the water pump to drive the A.I.R. pump. This was an add on pulley that was used along with the two groove water pump pulley.
3991423 was the water pump pulley for cars without AC, and is described as being a 2 groove pulley, 5 13/16" in diameter. This pulley was used on 71-77 350's without AC, and on all 78-80's with the L-82 350.
3991424 was the pump pulley for cars with air conditioning. I know it was two groove, but the Parts Book doesn't give the dimensions for this pulley, but from other information I have I believe it was 6 1/8" diameter. It was listed for use on 71-74 350's.
Because 74 L-82's came with A.I.R. they also used a second, single groove pulley on the water pump to drive the A.I.R. pump. This was an add on pulley that was used along with the two groove water pump pulley.
