Corvette Water Pump Pulley Not Lining Up!

[PJ]

Every time I get up to about 3,000rpm in the Corvette (1973, 350, auto) the belts start squealing.  At first I thought it was just the power steering pump that wasn't aligned right but after looking more closely at it, the problem is actually the water pump pulley.  The pulley is too far forward, towards the front of the car, causing everything to be off p/s, alt and crank.  Its only maybe a 1/4 of an inch off but thats enough.

Corvettes have a somewhat special water pump it is like a "short" water pump however the shaft is 3/4" (I think normal is 5/8").  I learned that tid bit last year when buying a new clutch fan, you have to buy one for this specific water pump not a more generic one.  So because of that I know I have a Corvette pump.  So then I took a look at the pulley itself and the part number stamped on it is 3991423.  This is the correct pulley for a 70's smallblock Corvette without A/C..... so why won't this line up?

100% the pulley has to go back, towards the engine.  Is my problem the wrong pulley or something with the water pump?

I did some research to see what other problems people have had and found some people with the same problem but no one ever listed what their solution was.  I am going to look at my Corvette manual tomorrow.  I am hoping it has some dimensions of the water pump (or pulley) so I can check that mine is correct.  I was debating on trying a pulley for a vehicle with A/C.  I am not sure what the differences are but figured its worth a shot.  Until I saw the prices, about $150-$175 USED.  

If I figure it out, I'll update.


You can see the belt on both the P/S and the alt are on the left edge of their pulleys.


At the water pump pulley you can see both belts on the right edge.  Also the water pump has an indentation at the top making me think the pulley is supposed to be sitting further back, otherwise whats the point of that indentation?

[Yukon]

It would appear that you have a pulley alignment problem from the pictures.

My question is when did it start making noise? After the pulley change/reinstallation?

Does the water pump pulley turn true-no wobble?

A temporary solution may be new belts just due to their greater pliability which could help keep the squeal down due to the angle of rotation. Obvious statement here, but old belts harden considerably when they age and dry out, especially those old V-belts.

It also wouldn’t surprise me if you find out either your water pump or pulley was manufactured incorrectly even if the part number matches the Vette listing.

I am interested to know what you find.

[PJ]

It would appear that you have a pulley alignment problem from the pictures.

My question is when did it start making noise?  After the pulley change/reinstallation? 

Does the water pump pulley turn true-no wobble? 

A temporary solution may be new belts just due to their greater pliability which could help keep the squeal down due to the angle of rotation. Obvious statement here, but old belts harden considerably when they age and dry out, especially those old V-belts.

It also wouldn’t surprise me if you find out either your water pump or pulley was manufactured incorrectly even if the part number matches the Vette listing.

I am interested to know what you find.

The belt(s) have pretty much always made noise I think they have just gotten worse.

The pump pulley doesn't wobble at all.

I took another look at it today.  Someone on Instagram suggested the water pump could still be wrong because their is a heavy duty truck version that is similar to the Corvette version (has the 3/4" shaft) but is a bit longer.  So I got the part number of the water pump, 330813 and that is the correct Corvette water pump.  

As I was looking at this thing I noticed the shaft that the flange/hub for the fan goes on was shiny between the pump and the flange.  And the shiny section looks to be just about exactly the amount my pulley is off.  So now I am thinking the pump was rebuilt at some point and the flange was not put back on the shaft all the way causing the pulley to be too far forward.  The flange is pressed on so I am not sure their is anyway to push it further onto the shaft without taking the pump off and apart.  A new pump is only $50, so I may just get a new one and not screw with it.

All that being said I had 2 new belts that I bought over the winter, I put those on and the squeaking has stopped for now.  You can still see the belt shooting off to the side and it kind of annoys me so maybe this winter I will mess around more with the pump but as long as the squeaking doesn't come back and I don't end up throwing a belt I am going to leave it alone for now.

(Next project is the windshield wipers.  Once they are fixed everything on the Vette will be 100% operational.)


330813, can't see the phone screen when taking the picture so it took like 10 tries to actually see the number.


I think if that flange was sitting back further the pulley would line up perfectly... I also need to replace those studs.

[Yukon]

Doubtful it’ll throw the belts unless you like to redline a 47 year old engine a lot. They will wear out faster due to the extra heat from the added friction.

I think you nailed the problem with that shiny section on the flange. I would certainly give pressing it on that much farther a shot first. I’d think finding a large socket that fits inside or outside the studs along with several GENTLE love taps from a ball peen hammer should do it without too much shock to the bearings. Nothin to lose.

[PJ]

Doubtful it’ll throw the belts unless you like to redline a 47 year old engine a lot. They will wear out faster due to the extra heat from the added friction.

I think you nailed the problem with that shiny section on the flange. I would certainly give pressing it on that much farther a shot first. I’d think finding a large socket that fits inside or outside the studs along with several GENTLE love taps from a ball peen hammer should do it without too much shock to the bearings. Nothin to lose.

Gentle being the keyword there.  Maybe torch the hell out of it first.  My worry is I'll be able to move it but it'll leak like a pig or I'll damage the bearing in the process.

The few times I have seen these messed with the flange is either put on with a press or a sledge hammer.

[Yukon]

Yeah, a press would be best. I was trying to think of a way to do it without taking the pump off, first.