1967 small block Water Pump (L79) Date code question - Original? Restore or Replace?

[Scott S.]

Trying to identify the water pump that was on the '67, to determine whether to have it restored/rebuilt, or do I need to find a correct water pump? The hub is wrong, but if the casting is correct, the hub might be replaced. I'm not sure how to interpret the "A 6 2" date code with this casting number.

Details:
1967 Coupe
L79 350hp
C60 air conditioning
Water Pump Casting Number: GM 11 over 3859326
Water Pump Date Code: A 6 2
Mounting hub has 8 threaded holes (should be only 4)

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Excerpts, 1967 JG, 4th edition, p. 85.

"The fan clutch mounting hub on all water pumps has only four threaded holes."

"The water pump has an alpha-numeric casting date... The format is MDDY. Example: "C127" = March 12, 1967.

"All non air conditioning engines use a water pump nipple with a wide hex center section. Air conditioning equipped engines use a water pump nipple which is shorter in length to allow additinal clearance. Both nipples are cadmium or zinc plated."

"L79 350 hp
All engines use water pump casting number 3859326 with a 5/8-inch opening for the bypass fitting which is a cadmium or zinc plated 87-degree elbow. Judge any 3859326 pump with a larger opening as a replacement."
~~~~~~~~~~~~~~~~~~~~

72?





Water pump | Regular | W855 (store part number?) | Dayton Parts Company | $22.75 | 6-27-79

[William C.]

Re: 1967 small block Water Pump (L79) Date code question - Original? Restore or Repl

It's a 1972 pump and it has a 3/4 to 5/8 reducer for the bypass hose.

[Joe L.]

Re: 1967 small block Water Pump (L79) Date code question - Original? Restore or Repl

Trying to identify the water pump that was on the '67, to determine whether to have it restored/rebuilt, or do I need to find a correct water pump? The hub is wrong, but if the casting is correct, the hub might be replaced. I'm not sure how to interpret the "A 6 2" date code with this casting number.

Details:
1967 Coupe
L79 350hp
C60 air conditioning
Water Pump Casting Number: GM 11 over 3859326
Water Pump Date Code: A 6 2
Mounting hub has 8 threaded holes (should be only 4)

~~~~~~~~~~~~~~~~~~~~
Excerpts, 1967 JG, 4th edition, p. 85.

"The fan clutch mounting hub on all water pumps has only four threaded holes."

"The water pump has an alpha-numeric casting date... The format is MDDY. Example: "C127" = March 12, 1967.

"All non air conditioning engines use a water pump nipple with a wide hex center section. Air conditioning equipped engines use a water pump nipple which is shorter in length to allow additinal clearance. Both nipples are cadmium or zinc plated."

"L79 350 hp
All engines use water pump casting number 3859326 with a 5/8-inch opening for the bypass fitting which is a cadmium or zinc plated 87-degree elbow. Judge any 3859326 pump with a larger opening as a replacement."
~~~~~~~~~~~~~~~~~~~~

72?





Water pump | Regular | W855 (store part number?) | Dayton Parts Company | $22.75 | 6-27-79

Scott-----


The GM #3859326 casting was manufactured for SERVICE long after it was last used in PRODUCTION (i.e. 1967 for passenger cars and 1970 for some MD/HD trucks). So, I'd say your casting is dated 1972 or 1982. It might even be 1992 but I think the '326' casting was out-of-production by then.

The "dual pattern" hub and 3/4" NPT bypass fitting also strongly imply a SERVICE heritage for this pump.

You could look for a properly dated '326' casting with original 1/2" NPT by-pass fitting. However, you'll probably have to pay big $$$$ for it.

You could also carefully and cleverly install a 3/4" to 1/2" bushing in the bypass fitting so that it's indiscernable. I don't think the dates can be seen with the pullies installed and I don't think it's judged. And, no one will ever know it has a dual pattern hub.

[Scott S.]

Re: 1967 small block Water Pump (L79) Date code question - Original? Restore or Repl

Thanks William and Joe, much appreciated!