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	1964 1965 1966 1967 1968	283 195hp/220hp - 327 250hp/300hp 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.

Small block 'short' water pump