1964 water pump pulley

[Greg H.]

Having trouble verifying I have the correct water pump pulley. Mine is not lining up with the crank pulley which is correct.

The JM is very unclear as to part numbers for the water pump pulley. I have the 300HP non-AC engine.


First, it states all non AC cars have a pulley 7-1/2 in. diameter.


Then, while discussing AC cars, gives the part number 3850680 with no diameter (but a search has shown 6-1/4).

Can anyone confirm the dimensions and part number for the correct 64 water pump pulley for 300HP engine without AC? I need the diameter and also the offset (total height will be fine).

[Greg H.]

Re: 1964 water pump pulley

The pulley I have is GM 3790356 (6-1/8 dia.) and does not line up correctly with crank pulley which is correct.

[Joe L.]

Re: 1964 water pump pulley

The pulley I have is GM 3790356 (6-1/8 dia.) and does not line up correctly with crank pulley which is correct.

Greg------


The GM #3790356 is the correct waterpump pulley for your application. The crank pulley should be GM #3744043.

Your pulley alignment problem may be due to an incorrect waterpump hub spacing.

[David L.]

Re: 1964 water pump pulley

[Greg H.]

Re: 1964 water pump pulley

Best I can measure with the pump mounted on the car, it is matching this spec. Everything seems to add up. So I'm wondering if the harmonic balancer may be installed wrong.

[Timothy B.]

Re: 1964 water pump pulley

Greg,

If you have a camera post a picture and someone may have a suggestion.

[Joe L.]

Re: 1964 water pump pulley

Best I can measure with the pump mounted on the car, it is matching this spec. Everything seems to add up. So I'm wondering if the harmonic balancer may be installed wrong.

Greg-------


About the only way the harmonic balancer could be installed improperly that would affect pulley alignment would be if it was not pressed on far enough. In that case, the crank pulley would beforward of the waterpump pulley.

Insufficient press-on would be a real possibility in your case as your engine uses a non bolt-on type of balancer. Therefore, your crankshaft does not have a tapping for a bolt OR for a balancer installation tool. This means that the balancer has to be installed by impactive force (i.e. pounding it on with a hammer). This makes balancer installation much more problematic.

[Chris D.]

Re: 1964 water pump pulley

The chart shown earlier misses the fact that the Corvette came with two variations of pump hub location. The larger dimension shown for Corvette on the chart applies to the solid lifter, high horse, deep pulley engines that were specific to the Corvette. The 250 and 300 horse power engines came with different pumps with the hub set up to the smaller dimension shown for regular passenger cars. The 63 service manual clearly shows two different dimensions depending on engine. It references different gauge tools without giving an actual dimension. The later chart provides the dimensions but misses the Corvette 250/300 use. You don't quite get the whole story from either source.

Is your water pump pulley too far forward by 1/8" ?

[Greg H.]

Re: 1964 water pump pulley

The chart shown earlier misses the fact that the Corvette came with two variations of pump hub location. The larger dimension shown for Corvette on the chart applies to the solid lifter, high horse, deep pulley engines that were specific to the Corvette. The 250 and 300 horse power engines came with different pumps with the hub set up to the smaller dimension shown for regular passenger cars. The 63 service manual clearly shows two different dimensions depending on engine. It references different gauge tools without giving an actual dimension. The later chart provides the dimensions but misses the Corvette 250/300 use. You don't quite get the whole story from either source.

Is your water pump pulley too far forward by 1/8" ?

Chris,
I think you just answered my question. I have to put the pulleys back on to measure but it was about 1/8 inch, possibly a bit more but pretty close by eye. Being the fan pulley is the one too far forward then this must be the issue. I guess I have to confirm the dimension, remove the pump, and press the hub down to get where I need to be.
Thanks,
Greg

[Chris D.]

Re: 1964 water pump pulley

Greg,
If you do end up moving the hub, be sure to remove the backing plate and press against the shaft, not the casting legs. Some searches on the subject will yield more details from those who have done this.

Chris

[Douglas L.]

Re: 1964 water pump pulley

Greg,
If you do end up moving the hub, be sure to remove the backing plate and press against the shaft, not the casting legs. Some searches on the subject will yield more details from those who have done this.

Chris

I second that, I tried it and was searching ebay for a date correct core the next day.

[Greg H.]

Re: 1964 water pump pulley

Here are pics of the situation. The gap is pretty serious. Also it looks like the pulleys are very close together but evidently this is not a problem.

Could it be a problem with the Harmonic Balancer? Any way to confirm it is in the right position?

I realize I have a mis-matched bolt. Need to find another correct one somewhere.

[Joe L.]

Re: 1964 water pump pulley

Here are pics of the situation. The gap is pretty serious. Also it looks like the pulleys are very close together but evidently this is not a problem.

Could it be a problem with the Harmonic Balancer? Any way to confirm it is in the right position?

I realize I have a mis-matched bolt. Need to find another correct one somewhere.

Greg-------


I cannot see how this could be a problem with the harmonic balancer. The only possible way that could be is if the balancer hub extension had been ground down by a significant amount. I just cannot conceive of a reason that this would have been done. What's more, from what I can see the balancer is in about the correct position relative to the timing tab and timing cover.

Are you sure that the waterpump pulley is a GM #3790356?

By the way, the mis-matched balancer pulley bolt is a place bolt. This is an unusual type of bolt rarely used on Corvettes. In fact, the only application I know of for a place bolt on a Corvette was the caliper half clamp bolts on first design calipers used for 1965-E67 Corvettes. This bolt could not have been used for that application, though.

[Greg H.]

Re: 1964 water pump pulley

Thanks, Joe. Yes, I am sure the pulley is 3790356. I am glad you have ruled out the HB.

[Joe L.]

Re: 1964 water pump pulley

Thanks, Joe. Yes, I am sure the pulley is 3790356. I am glad you have ruled out the HB.

Greg-------


Then, I'd say it's got to be a waterpump hub spacing problem,