The water pump wizards over at Tuff Stuff Performance field a ton of questions about things like pump sizes, flow rates, belt routing, and all sorts of other cooling-related issues.

They shared the questions customers most often ask them about water pumps. It’s a good read if you’re looking at replacing or upgrading your current mechanical water pump.

Q: I installed a new water pump in my car but it’s still running hot. Why?

A: Engines that have been modified for more horsepower generally run hotter than stock engines. You might look into a pump with a greater flow rate than the stock pump, like Tuff Stuff’s Supercool water pumps. If combined with the proper thermostat and radiator, your engine’s overheating problem can be resolved.

Q: How do I know when I need a reverse-rotation water pump?

A: Typically, if you’re able to select a water pump by your vehicle or engine’s year/make/model, you can be sure that the water pump will be an exact replacement for your vehicle. If that’s the case, you shouldn’t have to worry about whether or not it’s reverse-flow.

If you’re building an engine or upgrading from a V-belt pulley to serpentine, you need to assess your situation further.

As a general rule, most serpentine systems require a reverse water pump.

You can determine this by seeing how the belt travels around the water pump pulley. If the back of the serpentine belt travels around the water pump pulley, you will need a reverse water pump.

If the inside of the belt travels on the water pump pulley, you will require a standard rotation water pump. Most pulley and bracket manufacturers can tell you what style of water pump you need for their system.

Q: What are the advantages of an aluminum water pump?

A: Some water pumps are available as aluminum rather than cast iron.

Aluminum pumps are much lighter than cast iron and can be polished to a high luster without rusting.

Q: How do you measure the height of a water pump?

A: “Hub height” is the industry term for measure a water pump’s height.

The hub height is a critical belt-alignment dimension determining where the water pump pulley belt groove(s) fall in relation to your crank, alternator, power steering pump and air conditioning pulley grooves.

The dimension from the mounting gasket surface to the outside face of the hub (where the pulley is bolted) is the hub height.

For example, it is especially helpful to know what the hub height dimension is to determine whether your Chevy water pump is a long- or short-style. A long or short water pump may be used on any Chevy V8 (Gen. I SB-Gen. II BB) engine as long as the correct pulleys are used and the belts are in alignment.


Measure from the top fan hub surface to the water pump mounting surface. (Image/Tuff Stuff)

Never attempt to press or pull the hub to change its dimension. This may result in an unbalanced fan blade that can explode the pump and cause serious injury. Water pumps can be special-ordered with a specified hub height or shims can be purchased to adjust the pulley outward in small increments.

Click here to find more water pump tech tips.

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