Water Pump

The casting code on a water pump is simple to decode. It includes the month, day and year such as J257. This decodes to October 25, 1967. Month codes are A through L for January through December. Beginning in 1970, big block water pumps used a two-digit year code to identify the year such as B12●72 would be February 12, 1972.

V8 Water Pump Casting Month Codes
A - January B - February C - March D - April
E - May F - June G - July H - August
I - September J - October K - November L - December

Two basic styles of water pumps were used in V-8 Chevelles from 1964 to 1972. Naturally, the small block engine (283/307/327/350) and the big block engine (396/402/454) used different pumps but both used short and long styles. The 'short pump' was used from 1964 through 1968 and the 'long pump' from 1969 through 1972.  Not only did casting numbers change but designs changed to accommodate accessory brackets.

The following list may not be 100% complete due to difficulty in researching an item such as a water pump that has probably been changed numerous times over the car's lifespan.

Pump Casting Year Engine

Small Block

3782608 1965
1966
1967
1968
283 195hp/220hp - 327 250hp/300hp
283 195hp/200hp - 327 275hp
283 195hp - 327 275hp
307 200hp - 327 275hp/350hp
3859326 1965
1966
1967
327 350hp
327 350hp
327 325hp
3927170 1969-1971 All SBC
3953692 1969 307 200hp - 350 250hp, 255hp, 300hp
3927170 1970-1971 All SBC
3953692 1970-1971 All SBC
6263701 1972-1975 All SBC
Big Block
3856284 1965
1966
1967
1968
396 375hp
396 325hp, 360hp, 375hp
396 325hp, 350hp, 375hp
396 325hp, 350hp, 375hp
3931065 1969 396 325hp, 350hp, 375hp
3931065 1970 (early) 402/454 (All)
3969811 * 1970 (late) - 1971 402/454 (All)
6263707 1972 402/454

Depending on whose measurements you believe, you can still see the differences between the short and long water pumps in the photos below. Also remember that all small block water pumps and all big block water pumps will physically bolt up to their respective engines and will work quite well assuming the associated brackets (A/C, P/S, Alt., etc.) are used.  Depending on the size of your hand you should be able to put your fingers easily between the back of the water pump and the timing cover on a long water pump but not a short water pump.

 CHEVELLESTUFF  All Rights Reserved
Small block 'short' water pump

 CHEVELLESTUFF  All Rights Reserved
Big block 'short' water pump

CHEVELLESTUFF  All Rights Reserved
Small block 'long' water pump

CHEVELLESTUFF  All Rights Reserved
Big Block 'long' water pump

Examples

CHEVELLESTUFF  All Rights Reserved
Casting number 3856284 and date C 31 5 - March 31, 1965

CHEVELLESTUFF  All Rights Reserved
Casting number 3856284 and date K 1 6 - November 1, 1966

CHEVELLESTUFF  All Rights Reserved
Casting number 3856284 and date H 17 7 - August 17, 1967

CHEVELLESTUFF  All Rights Reserved
* Casting number 3969811 and date K 11 9 - November 11, 1969 (found on December 1970 LS5).

Courtesy Bill Hall
Casting number 3969811 and date I 1 71 - September 1, 1971

CHEVELLESTUFF  All Rights Reserved
CHEVELLESTUFF  All Rights Reserved
Casting number 6263707 and date I041-1 believe to be September 04, 1971; extra -1 is unknown.

CHEVELLESTUFF  All Rights Reserved
Another 6263707 1972 water pump. Note the date format is different - A5●72 for January 5, 1972.