Water pump pulley spacer question

[powerwagontim]

I have a cast pot metal spacer, 3/4" thick. It would appear to go between the water pump pulley and the fan, to push the fan forward. I cant see why the fan needs to move forward, it does not appear to interfere with anything when the spacer is removed. Also, the parts manual shows a thin steel spacer in between the water pump hub and the back of the pulley. Is this optional? If I install the steel spacer, it throws the main pulley and the water pump pulley out of alignment by the thickness of the spacer. I am inclined to not use either one, but there is a good chance I am not seeing something obvious in front of my face.
Thanks,
Tim

[Lifer]

All water pumps not being equal, the spacers are probably there to compensate for variations in their shaft lengths. The thin steel spacers can be added or removed as necessary to line up the pulley grooves for optimum belt wear. The thicker cast spacer could have been used to move the fan closer to the radiator if the engine had a history of running hotter than desired. These are things to consider when replacing a water pump, but most hobby mechanics are either unaware of them or just don't bother. I've replaced many water pumps in the last 50 years, and have found more than one or two which had their pulleys out of alignment.

[cuz]

It is a common practice when the vehicle has no shroud or the shroud is missing to move the fan closer to the radiator.

[M37UK]

I had to put spacers on mine to stop the fan hitting the power steering pump pulley.

Stu

[MSeriesRebuild]

I have a cast pot metal spacer, 3/4" thick. It would appear to go between the water pump pulley and the fan, to push the fan forward. I cant see why the fan needs to move forward, it does not appear to interfere with anything when the spacer is removed. Also, the parts manual shows a thin steel spacer in between the water pump hub and the back of the pulley. Is this optional? If I install the steel spacer, it throws the main pulley and the water pump pulley out of alignment by the thickness of the spacer. I am inclined to not use either one, but there is a good chance I am not seeing something obvious in front of my face.
Thanks,
Tim

The spacer you have sounds like original equipment, the newer style replacement water pumps have a different hub (shorter) that requires the spacer thickness be reduced by half or to 3/8" thick. Check this out and see if that won't get it lined up correctly. We have machined many to accomplish this. It allows the hub to engage the fan bore so it centers and isn't just hanging on the mounting bolts.

[powerwagontim]

Hi Charles,
My pulleys align well, without any spacer behind the pulley. The fan does not interfere with anything without the cast spacer. Is it a problem just eliminating the outer spacer and having a bit of hub sticking through the fan? You are correct, with the cast spacer, the fan is out past the hub and hanging on the bolts.
Thanks,
Tim

[Lifer]

It won't hurt anything, and if you still have a shroud on your radiator you shouldn't have an overheating issue.

[MSeriesRebuild]

Hi Charles,
My pulleys align well, without any spacer behind the pulley. The fan does not interfere with anything without the cast spacer. Is it a problem just eliminating the outer spacer and having a bit of hub sticking through the fan? You are correct, with the cast spacer, the fan is out past the hub and hanging on the bolts.
Thanks,
Tim

As long as the fan has centered support and doesn't hit anything on the back side, these are the main issues. The farther forward the fan blades are inserted into the shroud, the more air flow the fan will pull through the core, which translates into the more, the better. The ideal condition will be this, use as much spacer thickness to shift the fan as far forward as you can without moving the center bore off the hub, that is the optimum set up.