For decades, limited development in water pump technology equated to a pretty straight-forward proposition for garage builders: Only one water pump fits your engine, so that’s the one you can use on your build without turning it into a much bigger project. While simplicity can be a virtue in some cases, lacking choice in parts selection is rarely a good thing.
Fortunately, in more recent years, the trickle-down effect of racing and high-end exotic sports car development has resulted in some viable options becoming available to builders, like block-mounted electric, remote-mounded electric and remote mounted mechanical designs.
But that also presents a different set of problems – like how to decide which type of water pump design is best suited to a particular project while ensuring that this crucial component in the cooling equation is up to the task. With the help of Edelbrock, Moroso, and Davies Craig, we’ll take a look at these different options and help you determine what to choose for your ride.
The most popular design by a wide margin, block-mounted mechanical water pumps might not be particularly exotic when compared to the other options out there, but they do have some inherent virtues. Among those, wide availability is toward the top of the list, since the vast majority of production engines were originally designed to use a mechanical block-mounted water pump, and there is likely to be an option for you at your local parts store.
Being the oldest design doesn’t make this package particularly sexy, but mechanical block-mounted water pumps have been around for more than a century, and that means engineers have had plenty of time to fine-tune the design.
“Our pumps have been designed with circle track racing and overall high-performance in mind,” says Edelbrock’s Smitty Smith. “Our pumps typically flow about 20 percent better than the stock OEM piece, and all of our manufacturing and assembly is done here in the U.S. to make sure the quality is up to our standards.”
One of the reasons that block-mounted mechanical water pumps have stuck around for so long is their simplicity. Unlike electric units, this type of water pump is belt-driven, so there’s no need to install additional wiring in order to run the pump. “These are bolt-on parts, meaning you don’t have to change any pulleys, add mounting hardware, or wire up anything else to replace the stock component with our pump,” Smith added.
For a street car under typical use, block-mounted mechanical pumps also have the inherent convenience of automatically shutting off the water pump when the motor stops running. In addition, there is no need to find space for the installation and bolt-on additional mounting hardware since the engine already has a space allocated for the pump. And of course, being the simplest and most readily available option typically makes block-mounted mechanical water pumps the least costly option, allowing you to focus funds elsewhere when you’re building on a budget.
Like block-mounted mechanical water pumps, remote-mounted mechanical pumps rely on a belt system to spin the impeller in order to move coolant through the system. While that means that the pump’s operation is still tied to whether or not the engine is running (which can be a benefit or a drawback depending on your build’s needs), there are a few key advantages to remote mount systems.
Remoted-mounted mechanical pumps are particularly useful in motorsport applications where the block-mounting location might hinder access to engine components that are being serviced or swapped out regularly.
Having a remote mechanical setup can also be useful in road racing applications where a high output motor is often subjected to long periods of wide-open throttle use or when dealing with a tight engine bay. Here you get the durability of the mechanical design, the ease of access of a remote setup, and the inherent benefit of getting the pump away from the excessive heat generated by a motor in a racing environment. For a similar set of reasons, this is often the design that’s suggested for heavy-duty towing applications as well.
A mechanical water pump sends coolant through the engine only when the belt is turning, meaning that the operation and flow of engine coolant is strictly based on RPM. This limits the flow of the water pump at low engine RPM. -Josh Backes, Davies Craig
Electric Water Pumps
While electric water pumps generally do not have the same level of robust durability of their mechanical counterparts, there are a number of scenarios where their use is a good idea – if not necessity.
In the case of block-mounted electric pumps, packaging is one of the key advantages offered, as the pump will mount in the stock location, but it will take up significantly less space than its mechanical counterpart. In competition builds with forced induction and other additional components, space is often at a premium, and switching to an electric water pump could gain some room in comparison to a mechanical pump.
Electric pumps are also lighter than mechanical pumps, so if you are looking to take a few pounds out of the front of the car, this is another way to do so. “Electric water pumps weigh less than mechanical water pumps, so they are used when someone is trying to get every last pound that they can out of a car,” says Thor Schroeder of Moroso Performance.
“Our electric water pump for LS engines (PN 63566) is an example of an electric water pump that can accomplish many things,” Schroeder adds. “Our two billet aluminum adapters mount in place of the factory LS water pump, and this allows you to use our big block Chevy electric water pump in its place. This eliminates the bulky LS water pump, and replaces it with a more compact and cost effective unit. And, since it’s a BBC pump, you could then use big block accessories on an LS engine to further improve packaging and clean up the engine bay a bit as well.”
As mentioned earlier, while a mechanical water pump’s operation is tied to the drive belt, and therefore dictated by the engine speed and operation, electric pumps are not. “With an electric pump the water pump can be controlled to operate based on the engines temperature rather than RPM, providing higher amounts of coolant flow at lower RPM, or even after engine shutdown,” explains Backes. “And, because electric pumps aren’t powered by the engine’s drive belt, swapping one in to replace a mechanical unit can also provide a performance bump as well.”
“Over the years, we’ve discovered from our own research and feedback from engine builders that mechanical water pumps take a significant amount of power from the motor,” Schroeder points out. “Engine dynamometer tests prove that many water pumps produce severe drag on engines at high RPM, absorbing as much as 15 to 20 horsepower in some applications.”
Even when an electric water pump makes the most sense for your application, there are other considerations to take into account when choosing between a block-mounted unit and a remote electric water pump.
“We believe that a remote-mounted pump is the best choice for any build because of these reasons: performance, packaging, and overall ease of access,” Backes explains. “Heat soak from the vehicle’s engine can transfer into a block-mounted electric water pump motor and can choke down the performance of these pumps as much as 15 percent. Using a remote mount water pump provides better performance and longevity when compared to the traditional block-mounted water pumps because the component is moved away from the extreme heat generated by the engine, and that means the water pump is not subjected to heat soak.”
This sentiment echoed by the folks at Moroso as well, who point out that heat generated after engine shut down (where a mechanical pump would stop flowing coolant through the system) can cause issues beyond the longevity of the pump itself. “Heat soak is harmful is because it can lead to failed gaskets and cracked/warped cylinder heads, affect bearing life, etc. The electric water pump can keep the coolant still circulating, letting the engine components cool down at a gradual rate,” says Schroeder.
“Additionally, moving the pump from the stock location can also help to make space where you need it,” Schroeder added. In instances of engine compartment packaging issues, running a remote electric water pump can free up space in front of the engine when a big turbo or blower is being used, and remote water pumps can be the solution when a big engine is being transplanted into a space that was originally designed for a much smaller one.”
And what about durability? “Heat soak is the biggest killer of performance in an electric motor,” Backes says. “When we designed our electric water pump we took this into consideration, constructing the electric motor to be bathed in engine coolant, on the coldest part of the vehicle’s cooling system (at the exit of the radiator). This helps to push the life of our electric water pump well into the 7,000-hour range when used with our fan controller.”
“Moroso has customers using electric water pumps in street/strip applications that are over 20 years old with 60,000 miles on them,” says Schroeder. “We have had this type of customer call in, tell us how long and how many miles are on their Moroso electric water pump, and order replacement seals for the pump – not because the pump was leaking but because they were freshening up the vehicle’s engine and everything that is bolted to it.”
Making The Call
Ultimately, deciding which kind of water pump works for your build is something that has to be determined on a case-by-case basis. “When addressing a cooling system, the builder must take cost, packaging, durability, and performance into consideration,” Backes advises. “All of these factors will have an impact on what type of pump is to be chosen for use in a performance cooling system.”
A quick consult with the folks at Edlebrock, Moroso, Davis Craig, or one of their authorized dealers can point you in the right direction when sorting out cooling system components. While weight reduction and freeing up horsepower is certainly an attractive proposition – particularly in competition applications – an electric water pump isn’t necessarily the right call in certain situations, so it’s important to get a clear picture of your cooling system and the abuses it will see before jumping in with both feet.