You may notice that some of our power steering pumps look very similar, but are referred to as “bottom outlet” pumps. We’re going to give a quick breakdown of top vs bottom outlet, what it means, and why one may be more beneficial for your setup.
Firstly, all of our pumps operate the same – there is no difference internally. This means that any of our top or bottom outlet pumps can be customized to the same specifications regarding pressure and return hose connection types, flow rates, pressure capacities, and threaded or through-bolt mounting bosses. This means we have an incredible amount of configuration options to ensure our pump is a perfect fit for your accessory drive and performance needs.
What is the Difference?
Top vs bottom specifically references the orientation of the pressure port on the pump. The pressure port can be installed on either side of the valve channel, which you can see is the long bump on the pump’s housing.
On an integral reservoir pump, top outlet means the pressure port is oriented at the 12 o’clock position when the return port is oriented at the 3 o’clock position. (See below left)
Alternatively, using the same integral reservoir setup, bottom outlet means the pressure port is oriented at the 6 o’clock position when the return port is oriented at the 3 o’clock position. (See below right)
Top Outlet Pump
Bottom Outlet Pump
But… Pumps Mounts Differ!
However, keep in mind that different Type 2 power steering pumps can be mounted with different rotational positions. This means that the pressure port on a top outlet pump might not always be pointing at the 12 o’clock position. For example, let’s look at a C5/C6 Corvette power steering pump below. The Corvette pump is a top outlet design, but uses a remote (detached) reservoir setup. It has a unique mounting orientation on the pump bracket, so the entire pump is rotated over 90 degrees counter-clockwise from the integral reservoir pump orientation we discussed above. The pressure port on the Corvette pump actually points at the 7 o’clock position while the return port is at 10 o’clock.
Corvette Pump (Top Outlet)
LS1 Fbody Pump (Top Outlet)
The Reason for Choose Top or Bottom
The main reason for choosing a top vs bottom outlet pump is to have easy access and hose clearance for your pressure and return ports. Some accessory drives have pump mounting orientations that require either a top or bottom for proper clearance. The LS1 Fbody pump (see above right) has an integral reservoir and uses a top outlet pump that orients the pressure port to 9 o’clock. A bottom outlet would not be possible with this pump because the alternator sits very close to the pump at 3 o’clock and hose clearance would be an issue on that side.
Other accessory drives, both factory and aftermarket, allow for multiple pump possibilities. Our LS Truck Kits, for instance, can accommodate top or bottom outlet pumps with either remote reservoir or integral reservoir setups. So choosing the pressure orientation is more personal preference, rather than necessity.
Final Thoughts
If you aren’t sure which pump would work best in your vehicle, you can either call our phone support or submit a Custom Pump Form submission. We will help you evaluate your options, or provide recommendations on which is the best pump configuration and tuning to fit your needs.
