Modifiying Saginaw Power Steering Pump - Revive

Article originally from GM Truck Central by HellKnightHicks about modifying the Saginaw PS pumps. The article no longer works correctly so I will repost it here

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The modifications we will discuss here will work on just about any Saginaw style power steering pumps out there. If it’s got the flow piston, these modifications will work.

If you choose to perform any of these modifications, they are all done at your own risk.
Disassembly and Parts
First you need to pull the servo/valve assembly out of the power steering pump. This can be done with a 1” socket and an impact hammer.
Item A in the following photo is the portion of the pump that can be unscrewed.



After removal of the fitting you will see the flow piston. If it did not come out you can take it out with a magnet. There is a spring behind it, you will need to take that out also.

When removing it from the truck you should expect some, if not all, of the fluid to slowly drain from the pump.



When it all comes out it looks like this
A = Main fitting (The part the hose screws into)
B = Piston Spring
C = Flow Piston (Contains the High pressure Bypass)



Now onto the actual modifications

Idle/Low RPM Flow Modification


The fitting orifice controls the volume/speed that the pump can use to restore operating pressure (flow piston controlled). The larger the hole the more fluid the pump is able to use to respond the power steering pumps use of pressure.
Example: You turn steering wheel left. The gear box uses pressure built up in the system and the pump must restore pressure to the line. You will see it be very easy/quick at first few degrees of wheel rotation which slows shortly after as the pump is not able to keep the line pressure up.
Keep in mind that the pump can only pump so much at any given RPM, the assistance will always vary regardless of orifice size. But we can maximize the pumps ability to compensate in a timely manner.
You can use drill bits to determine the size of the opening inside of the main fitting. If you would like to make minor adjustments to gradually increase the size of the orifice.




If your fitting hole is smaller than 5/32 enlarge the hole to 5/32.


I have had the best results when drilling the fitting to 5/32. This seems to be a good spot for responsiveness without over-doing it. I may go larger at a later date but right now I’m content with 5/32 opening.
The 3500 hydro-boost power steering pumps have a 5/32.
The 1500 Pumps I have worked on have 1/8 had a much smaller orifice.
I have not been able to find information about orifices larger than 5/32. Please let us know of your experiences with larger orifices.

Increase Pressure Hold duration at Higher RPM’s
This spring keeps the flow piston pushed against the flow orifice.



Take the piston spring shown above. (This is the spring that sits outside the flow piston NOT the one from inside the flow piston)

Using a ruler or tape measure stretch this spring out to 2 ¼ inches. This will help the pump hold the pressure as the RPMs increase. The flow piston will still close but will reduce the speed at which it does so.
I have tested with a spring that was 2 ½ incheslong and it seemed to cause the flow piston to stick in the closed position. This was in combination with the end cap being screwed down with no spacers. Push the gas just a little and it pops lose…

Increase Pump Pressure
The flow piston controls the amount of pressure the system has. Pressure modifications will be done here.



Above are flow pistons from stock setups.
From left to right
Piston #1 and #2 are approximately 1100~1200 PSI
Piston #3 is a 1050~1100 PSI
Piston #4 is a 900~1000 PSI

-Precautions/Warnings
You can damage you Gear Box seals or blow hoses by increasing the pressure to much. Do understand if you have a car with 200,000 miles or many years on it that your hoses may be weak. If you have a leak before making changes here it WILL be worse. You may want to put new pressure lines on your setup before preforming the following modifications.
Increasing the pressure, without a doubt, will increase parasitic loss from the power steering pump. More pressure means more push but it also means it takes more power to run it.

-Disassembly
Place the flow piston in a vice, clamping the front and back outer rings, I put a nitrite glove around mine to help prevent scuffing. Heating it up with a propane torch can help loosen the loc-tight if you have any in it. Out of the ones I’ve taken apart, they were a little bit difficult but required no heating. Even though the piston is tough, I didn’t scratch any of them either.


Using a 7/16 wrench unscrew the end cap.


There’s a BB behind the end cap. Don’t lose it.