1965 Water Pump

[bill #36445]

Does anybody know if all 1965 327's used the same water pump or were there different pumps (with varying flow rates) based on the horsepower level of the motor. I have a '65 327/350hp with a water pump that is leaking from the front seal. My car is not a number's matching car so I'm not dead set on a correctly dated pump but I do want one that is correct for the car from a performance standpoint. Any help would be greatly appreciated. Thanks!

[Joe L.]

Re: 1965 Water Pump

Bill-----

There were 2 different waterpumps used for 1965 Corvette applications. These were of GM CASTING #3782608 and GM CASTING #3859326. These pumps differ only in the type of bypass provisions. The 3782608 uses internal bypass and was used with engines with cast iron intake manifolds. The 3859326 uses external bypass and was used with engines with aluminum intake manifolds.

You don't need to worry about pumping capacity, at all. All PRODUCTION GM small block waterpumps have, nominally, the same capacity. Most aftermarket or rebuilt pumps do, too. Although pumping capacity is not affected very much by impeller type, I prefer pumps with cast iron impellers rather than stamped steel. All PRODUCTION and SERVICE pumps built through about 1974, or so, used cast iron impellers. After about that time they changed to a stamped steel type.

[Joe L.]

Re: 1965 Water Pump

Bill-----

There were 2 different waterpumps used for 1965 Corvette applications. These were of GM CASTING #3782608 and GM CASTING #3859326. These pumps differ only in the type of bypass provisions. The 3782608 uses internal bypass and was used with engines with cast iron intake manifolds. The 3859326 uses external bypass and was used with engines with aluminum intake manifolds.

You don't need to worry about pumping capacity, at all. All PRODUCTION GM small block waterpumps have, nominally, the same capacity. Most aftermarket or rebuilt pumps do, too. Although pumping capacity is not affected very much by impeller type, I prefer pumps with cast iron impellers rather than stamped steel. All PRODUCTION and SERVICE pumps built through about 1974, or so, used cast iron impellers. After about that time they changed to a stamped steel type.

[Eugene B.]

Re: 1965 Water Pump

Bill,
I just purchased a very nice ...608 pump with cast iron impeller from Bill Mock for my '65, 250 hp. He advertises in the Driveline.

My thoughts are if you're going to buy a water pump anyway, you might as well buy one that has the correct casting date for your engine. It won't cost any more.

Good luck with your '65.

Regards,
Gene

[Eugene B.]

Re: 1965 Water Pump

Bill,
I just purchased a very nice ...608 pump with cast iron impeller from Bill Mock for my '65, 250 hp. He advertises in the Driveline.

My thoughts are if you're going to buy a water pump anyway, you might as well buy one that has the correct casting date for your engine. It won't cost any more.

Good luck with your '65.

Regards,
Gene

[Jack W.]

Re: 1965 Water Pump

seem to recall no casting date being on the 65 water pump, meaning it is not an issue to be concerned with (aside from not wanting to get one that DID have a casting date on it) . . . if I am wrong I am sure I will promptly corrected, happens all the time at home

[Jack W.]

Re: 1965 Water Pump

seem to recall no casting date being on the 65 water pump, meaning it is not an issue to be concerned with (aside from not wanting to get one that DID have a casting date on it) . . . if I am wrong I am sure I will promptly corrected, happens all the time at home

[Eugene B.]

Re: 1965 Water Pump

Jack,
I'm looking at the water pump that is going on my '65. On the side where the heater hose nipple is, there is a large GM and a mold number. Under the GM is the casting number 3782608. On the opposite side is the date code A205 for January 20, 1965. At least I hope that's what it means.

The date code can be seen easily behind the bell pulley. The casting number is covered by the pulley.

Best regards,
Gene

[Eugene B.]

Re: 1965 Water Pump

Jack,
I'm looking at the water pump that is going on my '65. On the side where the heater hose nipple is, there is a large GM and a mold number. Under the GM is the casting number 3782608. On the opposite side is the date code A205 for January 20, 1965. At least I hope that's what it means.

The date code can be seen easily behind the bell pulley. The casting number is covered by the pulley.

Best regards,
Gene

[Jack H.]

Solution is in the new JG book....

The 5th edition of the 1965 Judging Guide adds reference notes clarifying the issue of water pump casting dates. They state casting dates began approx March, 1964 for the '208 housing, November, 1965 for the '326 casting and BB pumps were cast date coded from the git go.... Note, both SB water pumps would have been made in the Saginaw/Flint complex while BB pumps would have come from Tonawanda.

[Jack H.]

Solution is in the new JG book....

The 5th edition of the 1965 Judging Guide adds reference notes clarifying the issue of water pump casting dates. They state casting dates began approx March, 1964 for the '208 housing, November, 1965 for the '326 casting and BB pumps were cast date coded from the git go.... Note, both SB water pumps would have been made in the Saginaw/Flint complex while BB pumps would have come from Tonawanda.

[Jack W.]

Re: 1965 Water Pump

Thanks Jack H. - that's why I had it in my head about the "no casting date" for the 65 water pump - because I have an L76 and as the handy-dandy TIM&JG confirms, the L79, L76 and L84 got the '326 (with the by-pass) other applications (base and L75) got the '608, and as the TIM&JG points out, '326 water pumps did not begin to have a casting date until Nov. '65, thus no casting dates on '326 water pumps for the '65 M.Y. Gene, yours is for a base or 300 hp L75, and you are good with the date, sorry if I created confusion for you.

[Jack W.]

Re: 1965 Water Pump

Thanks Jack H. - that's why I had it in my head about the "no casting date" for the 65 water pump - because I have an L76 and as the handy-dandy TIM&JG confirms, the L79, L76 and L84 got the '326 (with the by-pass) other applications (base and L75) got the '608, and as the TIM&JG points out, '326 water pumps did not begin to have a casting date until Nov. '65, thus no casting dates on '326 water pumps for the '65 M.Y. Gene, yours is for a base or 300 hp L75, and you are good with the date, sorry if I created confusion for you.

[bill #36445]

Re: 1965 Water Pump

Joe;

Thanks for the information regarding the two styles of pump. My car, though it is a 350hp, has the 608 pump on it. I assume one of the previous owners installed the wrong pump. Does it matter if you use a pump without the external bypass line on a car with the aluminum intake? My intake is the correct aluminum casting 3844461 but the bypass port has a plug installed.

At this time, I'm not 100% concerned about matching casting numbers since I just want to get the car running so that I can enjoy it (I just brought it home last week). I do plan to restore the car in a few years so I'll be sure the put the correct pump casting and bypass hose on it at that time. Am I okay to run the car without the bypass line installed? I just bought a replacement pump at a local parts store here in Canada ($40 Canadian) and it does have provisions for an external bypass line but I do not have the fittings or the hose since my car had the 608 pump on it when I got it. At this time I have a plug in the bypass ports on both the pump and the intake. Parts are very difficult to come by up here in the Great White North so I'll likely have to order anything I need from a supplier in the U.S. but I'd like to be able to drive the car while I wait for the bypass hardware to arrive. Any thoughts would be greatly appreciated.

Thanks,

Bill Jennings #36445

[bill #36445]

Re: 1965 Water Pump

Joe;

Thanks for the information regarding the two styles of pump. My car, though it is a 350hp, has the 608 pump on it. I assume one of the previous owners installed the wrong pump. Does it matter if you use a pump without the external bypass line on a car with the aluminum intake? My intake is the correct aluminum casting 3844461 but the bypass port has a plug installed.

At this time, I'm not 100% concerned about matching casting numbers since I just want to get the car running so that I can enjoy it (I just brought it home last week). I do plan to restore the car in a few years so I'll be sure the put the correct pump casting and bypass hose on it at that time. Am I okay to run the car without the bypass line installed? I just bought a replacement pump at a local parts store here in Canada ($40 Canadian) and it does have provisions for an external bypass line but I do not have the fittings or the hose since my car had the 608 pump on it when I got it. At this time I have a plug in the bypass ports on both the pump and the intake. Parts are very difficult to come by up here in the Great White North so I'll likely have to order anything I need from a supplier in the U.S. but I'd like to be able to drive the car while I wait for the bypass hardware to arrive. Any thoughts would be greatly appreciated.

Thanks,

Bill Jennings #36445