62 water pump pulley

[John F.]

Re: 62 water pump pulley

I'm stumped. The old pump fit just fine but started leaking and was a replacement of some sort. The new one is from Bill Mock.

[Joe L.]

Re: 62 water pump pulley

I'm stumped. The old pump fit just fine but started leaking and was a replacement of some sort. The new one is from Bill Mock.

John-----


It's a mystery, that's for sure. As I mentioned, there's no difference between the waterpump shaft centerline relative to the block for any of the samll block waterpumps used on Corvettes (and, as far as I know, for any other Chevrolet applications, either). Plus, the '609' waterpump was the one used for 1962 Corvettes.

Actually, it surprises me that the '609' was used for 250 hp and 300 hp 1962 applications since they did not use external bypass and the '609' is an external bypass-type pump. I would have expected that a GM #3782608 pump (i.e. non external bypass equivalent of the '609') would have been used. However, regardless, it should make no difference whether either pump was used relative to waterpump shaft centerline location.

[John F.]

Re: 62 water pump pulley

A friend who builds motors up in Mich recommended that I loosen up the water pump bolts a little and see if the pump shifts on the block in the bolt holes. He said there should be a few thousands of play in the bolt holes of the pump. Maybe just enough to make a difference. Any thoughts? Spoke w/Bill Mock. He said to try it. Also this is the correct pump but not sure if a new pulley would do it.

[Joe L.]

Re: 62 water pump pulley

A friend who builds motors up in Mich recommended that I loosen up the water pump bolts a little and see if the pump shifts on the block in the bolt holes. He said there should be a few thousands of play in the bolt holes of the pump. Maybe just enough to make a difference. Any thoughts? Spoke w/Bill Mock. He said to try it. Also this is the correct pump but not sure if a new pulley would do it.

John-----


There is enough clearance in the bolt holes of the pump to move it a small amount after loosening the bolts.

If both of the pullies are original GM pieces, it's hard to understand how they could be "off" in OD. However, if either is a reproduction, then that's another story.

Also, can you tell if the pump you got from Bill Mock is an original GM casting (i.e. does it appear to be an "old" and re-conditioned casting) or might it be some sort of "reproduction"? Although I don't know that any reproductions are made of the '609', it's possible and if it's a reproduction it might be "off" in a critical dimension.

[Mike B.]

Re: 62 water pump pulley

John,

As others have noted, there is little to no play or variation in the spacing between the centerline of the pump and that of the crank. So if you are absolutely sure that both pulleys are correct (look for the stamped numbers), then the only other suspect it the pump itself. I have never heard of that type variation in any original or replacement water pump, but with the flood of foreign and counterfeit parts out there, who knows?

So if you have the old pump that used to be installed, you might try dry fitting it with pulleys but sans fan all bolted up snug to prove it to yourself.

Attached is a photo of what I believe is a correct 609 pump. I fished it out of a mixed, rusted pile of parts at a swap meet about five years ago so I believe that it is the real deal. Sorry that it not the greatest photo, but maybe you might find something different on yours for a clue.

Mike

[Terry R.]

Re: 62 water pump pulley

John your problem is really working on me so checked the clearance between the two pullies(816 pulley on top). On mine the clearance is about .035 of an inch. Could the clearance between the bolts that attach the waterpump and their bores do it? Not much clearance but neither is .035. Maybe support the engine, loosen the bolts and pry the pump up as you're tightening the bolts. Just a long shot. Good Luck (hopefully you won't tear a gasket)

[Jack H.]

Re: 62 water pump pulley

Bill Mock is the original 'straight arrow' guy when it comes to water pumps. He knows well the difference between the various pump housing castings (GM Flint vs. Tonawanda + reproduction/service replacements) and would die a thousand deaths if he ever cut corners in supplying anything less than a real McCoy item...

About the only things I've seen that affect form/fit with these used/reconditioned pumps is:

(1) Incorrect press fit of the hub onto the pump shaft.

(2) Owner failing to install the reinforcement plate between the pump hub and the pulley.

(3) Original pump casting SO rusted/deteriorated that the rebuilder had to mill excess metal from the pump's attaching legs to obtain a flat/true surface for the gaskets to seat reliably.

The first two issues could affect pulley to pump body clearance. The third issue would simply make the pump's body 'shorter' affecting pulley to block clearance and pulley to pulley belt alignment...

[Mike B.]

Re: 62 water pump pulley

I would like to make it clear that I in no way meant to insult or implicate Bill Mock or anyone else regarding counterfeit water pumps; I was merely speculating in the absense of any other ideas. If it was construed that way then please accept my apologies.

Notwithstanding the above, after all of the opinions levied on this thread, I sure am anxious to learn the real reason for the problem.

[Dean R.]

Re: 62 water pump pulley

I measured the clearance between pulleys on two '62 engines with correct pulleys and waterpumps: Using a feeler gauge, 0.045" was a slip-tight fit on both.

[Mike E.]

Re: 62 water pump pulley

Just to correct a bit of misinformation--ALL 62 Corvettes, regardless of horsepower, used the 609 pump with the external bypass to the expansion tank mounted on the left-hand side.

[Joe L.]

Re: 62 water pump pulley

Just to correct a bit of misinformation--ALL 62 Corvettes, regardless of horsepower, used the 609 pump with the external bypass to the expansion tank mounted on the left-hand side.

Mike-----


Yes, I forgot about the "odd-ball" external bypass used for 1962. I think it was the only use of that style external bypass ever on a Corvette.

[Joe L.]

Re: 62 water pump pulley

I measured the clearance between pulleys on two '62 engines with correct pulleys and waterpumps: Using a feeler gauge, 0.045" was a slip-tight fit on both.

Dean-----


It must be that the actual OD of the pullies is slightly different than the GM published information. I have both of those pullies but I just used the published GM dimensions in my calculations since I didn't want to dig them out (actually, I tried to get at them but gave up). So, it looks like the actual OD's must be just a little greater and this is common with GM published information versus measured actual.

I have no recent direct experience with C1's but I am amazed, though, that the clearance between the pullies is 0.045". Normal manufacturing tolerances for parts like these could easily "eat up" that sort of clearance. I was even questioning my own calculations when I made them since I thought even 0.165" seemed unusually small clearance for a factory design. With the 0.045" clearance, it's easy now for me to understand how an interference problem could occur if any of the components or assembly were even slightly "off".

[Dean R.]

Re: 62 water pump pulley

Joe-

I also questioned whether the 0.045 clearance I observe is correct and adequate. It is anxiety producing. I note that Terry measured even less (in an above posting). I hope that John solves his problem and lets us know the resolution.

Dean

[John F.]

Re: 62 water pump pulley

It ate at me all night, so I pulled the pump off again and tried to compare the 609 pump to the one that was on it. I even took paint remover to the front of the pulley and low and behold it is a 816 pulley. I scraped all the old/new gasket off all surfaces and ran a dry run of the old and new pumps. One thing I did find was that the flange on the new pump needs to be pressed on about 1/16" more. I will recheck. There was a recent article in Corvette magazine about rebuilding a pump (Dec 2007). I will tackle re-assembly this weekend going very slow and methodical. Need to keep my fingers crossed as well. I'll post the results.

[Terry R.]

Re: 62 water pump pulley

John,

As others have noted, there is little to no play or variation in the spacing between the centerline of the pump and that of the crank. So if you are absolutely sure that both pulleys are correct (look for the stamped numbers), then the only other suspect it the pump itself. I have never heard of that type variation in any original or replacement water pump, but with the flood of foreign and counterfeit parts out there, who knows?

So if you have the old pump that used to be installed, you might try dry fitting it with pulleys but sans fan all bolted up snug to prove it to yourself.

Attached is a photo of what I believe is a correct 609 pump. I fished it out of a mixed, rusted pile of parts at a swap meet about five years ago so I believe that it is the real deal. Sorry that it not the greatest photo, but maybe you might find something different on yours for a clue.

Mike

I believe on an origional pump the casting number is on a slight arc where the reproduction is straight. Maybe one of the '62 experts can confirm.