Waterpump 101 for various applications:

Chevrolet: – “short vs. tall”.

This terminology applies to both small blocks & big blocks even though they use different waterpumps.  Prior to 1968 both engines will use the “short” style waterpumps.  In 1969 both engines use the “tall” waterpumps.  You can put your hand (or fingers) behind a tall waterpump.  A short waterpump is flush up against the timing chain cover.  You can switch waterpumps, but the waterpump will dictate the belt train on an engine.  In otherwords, a 1968 Chevelle 396 would have had a short waterpump.  If you use a tall waterpump on it – it will emulate a 1969 Chevelle and you’ll need to adjust all your accessory brackets and pulleys to the “1969″ style.

The Corvette uses the short waterpump.

The small block tall waterpump has another “FYI” associated with it.  There’s 2 styles… 1969 to 1976, and 1977+.  For the most part – they’re interchangeable, with the exception of how the power steering brackets will bolt to it.

Pontiac

Simply put – anything with 8 bolts is 1968 and older.  Anything with 11 bolts is 1969 and newer.

Oldsmobile:

The Olds used various lengths of waterpumps.   Getting the right pump is critical in retaining pulley/belt alignment. The difference is the distance between the block mounting surface and the pulley mounting on the hub

• YQ39 – 5 1/16″  (1968 – 70 w/o AC)
• YQ96 – 5.57″  (1971 – 1985 w/o AC)
• YQ44 – 5 9/16″  (1968 – 70 w/ HD cooling or AC)
• YQ46 & 305N – 5.95″  (1971 – 1988 w/ AC)

Generally cars with A/C and/or Heavy Duty cooling use a taller waterpump.  Make note of the year application, but order by height.

Mopar waterpump & housing Identification:

Knowing this information will come in handy when replacing a radiator or obtaining radiator hoses.  If you have a 1975 small block engine in a 1969 car – the waterpump will be aiming the hose toward the wrong side of the radiator.

Small block
1969 – earlier, cast iron, drivers side inlet
1970 – newer, aluminum, passenger side inlet
Internal impeller design will change by application.

Big block mopar

All waterpumps are the same externally.  Internally the impeller will differ depending on the application.

Big block waterpump housing
72 – earlier, drivers side inlet
73 – newer, passenger side inlet