C2 SHP Small Block Waterpump

[Steve F.]

Im going to need a waterpump soon. So my journey starts here to find the proper innards.

We know that these castings are what was used for the 65 327 engines.
3782608 - 250 & 300Hp engines
3859326 - 350,365, & 375Hp engines

But are the 65 SHP pump impellers different from the base models?

Steve

[Larry M.]

Re: C2 SHP Small Block Waterpump

No.

Larry

[Joe L.]

Re: C2 SHP Small Block Waterpump

Im going to need a waterpump soon. So my journey starts here to find the proper innards.

We know that these castings are what was used for the 65 327 engines.
3782608 - 250 & 300Hp engines
3859326 - 350,365, & 375Hp engines

But are the 65 SHP pump impellers different from the base models?

Steve

Steve------


The only functional difference between 250/300 HP and SHP small block waterpumps for the 1963-67 period was the pump body casting. The 250/300 HP has no upper boss for external bypass whereas the SHP pumps have an upper boss for external bypass. The impellers, bearing/shaft assembly, seals, rear plate and hubs are the same.

[Duke W.]

Re: C2 SHP Small Block Waterpump

Wasn't the hub that the pulley attaches to pressed on to a slightly different position on the shaft due to the dual belt arrangement on mechanical lifter engines?

Duke

[Larry M.]

Re: C2 SHP Small Block Waterpump

Wasn't the hub that the pulley attaches to pressed on to a slightly different position on the shaft due to the dual belt arrangement on mechanical lifter engines?

Duke

As far as I know, it was only different for those small block cars with factory AC and Power Steering (in 67 model year).

Larry

[Larry E.]

Re: C2 SHP Small Block Waterpump

Wasn't the hub that the pulley attaches to pressed on to a slightly different position on the shaft due to the dual belt arrangement on mechanical lifter engines?

Duke

Since I have switched several of my vehicles to use the "captured" belt for safety/reliability and have never had to adjust the
the hub on the pump itself; I believe the pulley(the way it is made) itself does all the adjustment for use of two belts. Picture below
is a LS9 for my pick-up. All I did was to install LT-1 pulleys and went right in using the same water pump/hub setup. JMHO>Larry

[Steve F.]

Re: C2 SHP Small Block Waterpump

Steve------
The only functional difference between 250/300 HP and SHP small block waterpumps for the 1963-67 period was the pump body casting. The 250/300 HP has no upper boss for external bypass whereas the SHP pumps have an upper boss for external bypass. The impellers, bearing/shaft assembly, seals, rear plate and hubs are the same.

Joe, Thanks for the confirmation. I did do some salvaging and concluded the same.

[Chris D.]

Re: C2 SHP Small Block Waterpump

Steve,

While the internal components are identical, the hubs are indeed set to different dimensions on the shaft. '63 shop manual specifies tool J-9608 as the fixture to set this dimension except for F.I. engines which are to use J-9648. Different tools, different dimensions.

Chris Davies

[Alan D.]

Re: C2 SHP Small Block Waterpump

The 3859326 has a drawing date of 5-18-65 so assure you're in the 6 month time frame

[Joe R.]

Re: C2 SHP Small Block Waterpump

As far as I know, it was only different for those small block cars with factory AC and Power Steering (in 67 model year).

Larry

To clarify the situation with the water pump flange placement, there were two types of pulleys used on C2 small blocks:

1) "Standard groove" pulleys used primarily on base engines
2) "Deep groove" pulleys used primarily on the high-hp SHP engines

The deep groove pulley sets required setting the pulley flange 1/8" farther out (toward the radiator) to line up with the corresponding deep groove pulley on the balancer.

The face of the balancer is in the same position on all C2 small blocks, so the face of the balancer is "ground zero" for pulley alignment. The center lines of the deep groove pulleys are 1/8" farther apart compared to the centerlines of the standard-groove pulleys, so the hub on the water pump has to be 1/8" farther out than the hub for the standard-groove pump.

What makes this confusing is that when a '66-'67 C2 small block SHP engines had BOTH air conditioning and power steering, GM used the standard-groove pulley set. So, these SHP engines (and only these SHP engines) had the standard-groove pulley set and the base engine placement for the water pump flange.

If you have alignment problems with your pulleys, it is usually because your water pump flange is in the wrong location and/or you have a mix of standard-groove and deep-groove pulleys. After a considerable amount of work, I think we have the pulley tables correct in the 7th edition of the 1967 JG.