Power steering pump valve assy control
Thread Starter
Melting Slicks
Joined: Sep 2006
Posts: 2,814
Likes: 469
From: Wichita Kansas
Power steering pump valve assy control
Is there a rebuild kit available for a stock power steering pump that includes the valve assy control? For a '72 350 automatic.
Thanks, I have had not luck finding one.
Thanks, I have had not luck finding one.
Race Director
Joined: Apr 2011
Posts: 11,183
Likes: 3,335
From: North of Toronto - Ontario
Are you talking about the pressure relief valve for the pump or the control valve for the steering ram?
I've never seen (or looked for) a separate pressure valve but they must be available somewhere, maybe check with a semi-local pump rebuilder or CSSB
on a side note, Jim SHea had a bunch of good info listed in a thread one time that I saves for when I eventually do my remote tank pump swap
C3 power steering system from 1968 through 1982 was the amount of flow (NOTE, NOT PRESSURE) that the various pumps produced. Here are the flows through the years:
1968-69 Max flow was 1.75 gallons per minute
1970-73 Max flow 1.60 gpm
1974-81 Max flow 2.90 gpm
1982 Max flow 1.9 gpm (probably reduced for improved fuel economy.)
Increased flow would tend to make the control valve more responsive and the effort would feel lighter.
Here would be one tip. If you can find a power steering pump from a known original 1974 through 1979 Vette, it will have the higher flow discharge fitting. You most likely don't want a 1980 and later discharge fitting because it would have a metric o-ring port and would require a special power steering hose assembly. Since all Vette pumps after 1974 had an interference fit pulley, all of them with a smooth driveshaft (except the 1980-1982 pumps) would have the higher flow discharge valves.
Another pump fact: The throat of the discharge fitting is a major controlling element as to the amount of oil that the pump discharges. It isn't quite as simple as just drilling out the throat of the discharge fitting. If you take a fitting out of the pump and look closely at it, behind the hex head is an o-ring. Just behind the o-ring at the bottom of the next groove (somewhere on the diameter) you will see a very small hole. That hole is called the P-hole and it communicates pressure back to the pump and regulates the flow control plunger behind the discharge fitting.
By going in and disturbing the diameters and surface finishes, you really don't know what you might end up with. But if you want to try, here is a guideline.
As a rule of thumb, for every 0.016 inch on the diameter that the throat is opened up, the pump will flow an additional 1/2 gallon per minute.
0.1144 inch throat diameter = 2.0 gallons per minute
0.130 inch throat diameter = 2.5 gallons per minute
0.144 inch throat diameter = 3.0 gallons per minute
Some people have complained about jerky steering when they have drilled out the fitting. They have disturbed the surface finish of the throat of the discharge fitting and/or may have caused a burr to cover the P-hole.
If you want more flow driving down the road, this will increase the flow from the pump. Obviously, once you open up the throat of the discharge fitting, there is no turning back.
One warning: The pressure relief on all C2/C3 Corvettes was set at 950 psi. A lot of GM steering systems have much higher pressure reliefs. The special Corvette power steering hoses were designed to operate with 950 psi max pressures. Changing the pressures that your Vette pump produces will cause hose leaks.
M
I've never seen (or looked for) a separate pressure valve but they must be available somewhere, maybe check with a semi-local pump rebuilder or CSSB
on a side note, Jim SHea had a bunch of good info listed in a thread one time that I saves for when I eventually do my remote tank pump swap
C3 power steering system from 1968 through 1982 was the amount of flow (NOTE, NOT PRESSURE) that the various pumps produced. Here are the flows through the years:
1968-69 Max flow was 1.75 gallons per minute
1970-73 Max flow 1.60 gpm
1974-81 Max flow 2.90 gpm
1982 Max flow 1.9 gpm (probably reduced for improved fuel economy.)
Increased flow would tend to make the control valve more responsive and the effort would feel lighter.
Here would be one tip. If you can find a power steering pump from a known original 1974 through 1979 Vette, it will have the higher flow discharge fitting. You most likely don't want a 1980 and later discharge fitting because it would have a metric o-ring port and would require a special power steering hose assembly. Since all Vette pumps after 1974 had an interference fit pulley, all of them with a smooth driveshaft (except the 1980-1982 pumps) would have the higher flow discharge valves.
Another pump fact: The throat of the discharge fitting is a major controlling element as to the amount of oil that the pump discharges. It isn't quite as simple as just drilling out the throat of the discharge fitting. If you take a fitting out of the pump and look closely at it, behind the hex head is an o-ring. Just behind the o-ring at the bottom of the next groove (somewhere on the diameter) you will see a very small hole. That hole is called the P-hole and it communicates pressure back to the pump and regulates the flow control plunger behind the discharge fitting.
By going in and disturbing the diameters and surface finishes, you really don't know what you might end up with. But if you want to try, here is a guideline.
As a rule of thumb, for every 0.016 inch on the diameter that the throat is opened up, the pump will flow an additional 1/2 gallon per minute.
0.1144 inch throat diameter = 2.0 gallons per minute
0.130 inch throat diameter = 2.5 gallons per minute
0.144 inch throat diameter = 3.0 gallons per minute
Some people have complained about jerky steering when they have drilled out the fitting. They have disturbed the surface finish of the throat of the discharge fitting and/or may have caused a burr to cover the P-hole.
If you want more flow driving down the road, this will increase the flow from the pump. Obviously, once you open up the throat of the discharge fitting, there is no turning back.
One warning: The pressure relief on all C2/C3 Corvettes was set at 950 psi. A lot of GM steering systems have much higher pressure reliefs. The special Corvette power steering hoses were designed to operate with 950 psi max pressures. Changing the pressures that your Vette pump produces will cause hose leaks.
M
Thread Starter
Melting Slicks
Joined: Sep 2006
Posts: 2,814
Likes: 469
From: Wichita Kansas
Thanks M, I had already read and reread Jim's paper with that information. I was looking for the pressure valve for the pump itself. Was thinking about removing the one on my pump and carefully over drilling it but if something went wrong, there I'd be. i may go to local junk yard and see if I can find a pump from a C10 or van or the like.
Last edited by kansas123; Apr 4, 2022 at 04:52 PM.
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From: mount holly NC
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Thread Starter
Melting Slicks
Joined: Sep 2006
Posts: 2,814
Likes: 469
From: Wichita Kansas
Oh man, I missed that part about the fitting assembly and the connector. I shall go hunt or one of those! Thanks
