Water pump pulley bent?
Thread Starter
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Water pump pulley bent?
I replaced my water pump in May, had to adjust the flange to make the pulleys line up. All was well.
Fast forward to last weekend, and the wp pulley is rubbing the wp housing and harmonic balancer. Last night I used a balancer installer to make sure it was fully seated, it didn't move very much, and the pulley was still rubbing on the wp housing. Could the flange have moved on it's own? Could the pulley be bent? There is some visible runout of the fore and aft edges of the pulley, but this is a stamped part so I wouldn't expect it to be perfect.
The wp pulley is a 3770245 7-1/8" deep groove (2 piece) w/reinforcement plate behind. I can't detect any cracks in the pulley. Has anyone seen wp pulleys bend over time?
Thanks
Fast forward to last weekend, and the wp pulley is rubbing the wp housing and harmonic balancer. Last night I used a balancer installer to make sure it was fully seated, it didn't move very much, and the pulley was still rubbing on the wp housing. Could the flange have moved on it's own? Could the pulley be bent? There is some visible runout of the fore and aft edges of the pulley, but this is a stamped part so I wouldn't expect it to be perfect.
The wp pulley is a 3770245 7-1/8" deep groove (2 piece) w/reinforcement plate behind. I can't detect any cracks in the pulley. Has anyone seen wp pulleys bend over time?
Thanks
Le Mans Master
Joined: Jan 2001
Posts: 6,746
Likes: 1,387
Compare your new waterpump to your old waterpump. When I installed a Flowkooler water pump on mine (ages ago) I noticed that it was "bulkier" than the old water pump. Since it was quite thick iron I just ground down on the water pump so the pulley wouldn't rub.....very slight grinding was required....it just "touched". It has been ok for 15.5 years.
Thread Starter
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Following up on this, it seems that indexing the pulley to the water pump shaft is a worthwhile exercise. I was able to reduce the amount of visible run out of the pulley just by changing its orientation relative to the mounting flange. I also added a 1/16" spacer behind the pulley (in addition to the reinforcement plate) to gain clearance to the water pump housing and harmonic balancer. So, I will run it like this and see what happens.
Here are a couple videos of the pulley with the engine running after indexing the pulley:
Here are a couple videos of the pulley with the engine running after indexing the pulley:
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Chris, it looks like you've fixed the problem and everything is running smoothly now. Great video's by the way. 
You didn't mention what water pump you installed. Was the pilot shaft the same diameter as the hole in the pulley? The Corvettes changed from a 5/8" pilot to a 3/4" pilot on the water pump in '73 I believe. If the pulley has the 3/4" hole and the water pump has a 5/8" pilot, it is possible that the pulley moved a bit, especially if the bolts that hold the fan hub loosened even a little.
What type fan are you using, a factory style clutch fan?
I have moved the pulley flange on a number of water pumps to get the alignment I desired. Typically they are so tight that it takes a press to move them so I've never found one to move.
Good luck... GUSTO
You didn't mention what water pump you installed. Was the pilot shaft the same diameter as the hole in the pulley? The Corvettes changed from a 5/8" pilot to a 3/4" pilot on the water pump in '73 I believe. If the pulley has the 3/4" hole and the water pump has a 5/8" pilot, it is possible that the pulley moved a bit, especially if the bolts that hold the fan hub loosened even a little.
What type fan are you using, a factory style clutch fan?
I have moved the pulley flange on a number of water pumps to get the alignment I desired. Typically they are so tight that it takes a press to move them so I've never found one to move.
Good luck... GUSTO
Thread Starter
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
The new water pump is a Delco 88926095 from Summit. 5/8" pilot so it is correct for the pulley. I did have to use a press to move the flange.
Fan is a stock 5-blade and the clutch is a Hayes unit, with a 1" spacer to provide clearance for the spreader bar. .
Fan is a stock 5-blade and the clutch is a Hayes unit, with a 1" spacer to provide clearance for the spreader bar. .
Thread Starter
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Update, the Delco water pump I installed late May/early June failed Saturday on my first run at an autocross. It lasted six events, for a grand total of 63.5 runs before failing completely. I was leary of the pump when it arrived and the box said made in China, don't buy the Delco 88926095!!!
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Update, the Delco water pump I installed late May/early June failed Saturday on my first run at an autocross. It lasted six events, for a grand total of 63.5 runs before failing completely. I was leary of the pump when it arrived and the box said made in China, don't buy the Delco 88926095!!!
I've also seen a few water pumps let go while autocrossing and take out a radiator.
The one your looking for is this Chevrolet Small Block Short Stage 2 - 22103
- Chevrolet Small Block - Short
- 1955-68 Passenger Cars
- 1955-72 Light Trucks
- 1955-70 Corvette
- 5.625" Length
- 3/4" Bearing
- 5/8" Shaft
- Clockwise Rotation
- High Flow Pump
- Cast Aluminum Finish
- Equal flow to left and right cylinder heads
- High flow and pressure
- 356-T6 heat treated aluminum specially ribbed casting
- Precision ground fan hub with dual bolt pattern
- Zinc-plated rear cover and bolts
- Two 1/2" NPT auxiliary inlets
- Machined for cam stop bolt (3/8-24)
- This casting also has extra material between the mounting holes to allow external pressure lines to be added
Chevrolet Small Block Short Stage 1 - 12103 The Stage 1 (Cast Iron) Water Pumps use new original equipment castings, but are machined and assembled by Stewart Components to exacting standards.
- Precision ground dual pattern fan hub for perfect pulley alignment
- High Flow Impeller
Good luck... GUSTO
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Thread Starter
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Thanks Gusto, I’ll look into that Stage 1 pump. Have to stay with cast iron to be legal for my class.
Also was considering having my previous pump rebuilt, it lasted almost ten seasons, not sure if anybody rebuilds water pumps anymore.
Luckily both water pump failures this year were not catastrophic.
Also was considering having my previous pump rebuilt, it lasted almost ten seasons, not sure if anybody rebuilds water pumps anymore.
Luckily both water pump failures this year were not catastrophic.
Last edited by 69autoXr; Sep 24, 2018 at 11:48 AM.
Le Mans Master
Joined: Sep 2003
Posts: 8,812
Likes: 2,029
From: eastern NC
Thanks Gusto, I’ll look into that Stage 1 pump. Have to stay with cast iron to be legal for my class.
Also was considering having my previous pump rebuilt, it lasted almost ten seasons, not sure if anybody rebuilds water pumps anymore.
Luckily both water pump failures this year were not catastrophic.
Also was considering having my previous pump rebuilt, it lasted almost ten seasons, not sure if anybody rebuilds water pumps anymore.
Luckily both water pump failures this year were not catastrophic.
Good luck... GUSTO
Thread Starter
Melting Slicks
Joined: Jan 2004
Posts: 3,247
Likes: 210
From: Detroit MI
Yes that does seem to have been the case. Funny thing was there was not much play in the bearing/shaft while trying to figure it out, but it was not a surprise when it failed. Bearing is basically seized up at this point.