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Power steering pump pressure

Mikel

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My '66 Olds has a type of Saginaw power steering pump that I wasn't familiar with. It is thicker (lengthwise) than the standard Saginaw PS pump every other vehicle out there has used for the last 40 years. The veins are longer too, I'm assuming for more volume.

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The pump relief valve kicks in at 1100 PSI. I added a couple of washers to the spring and now it's at 1200. Since I'm running a hydroboost unit, I'd like to bring it to 1500 PSI. Would shimming the spring further hurt the pump?

Thanks.
 

larboc

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How much line pressure does the hydro boost make with 1200psi PS fluid and what are you doing that needs more?
 

Mikel

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How much line pressure does the hydro boost make with 1200psi PS fluid and what are you doing that needs more?

It's just that from my reading, vehicles with hydroboost were set to that pressure, vs the standard 1100 PSI. But this was in trucks and mine is going in a car.
 

bdkw1

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I'd try the brakes before I cranked the pressure up.
 

Mikel

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I'd try the brakes before I cranked the pressure up.

One problem I have is that I put an XJ steering box in it (smaller piston than the stock one), which is normally fed 1500PSI max. At 1200 PSI, it is borderline adequate to turn the wheels of my car at a stop. I hope that an extra 300 PSI it will do it with no problems... Which should also make the HB happy.

Thanks.
 

larboc

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Try it and see? Worst case it grenades and you have to swap in a P-pump, or is that not an easy swap?
 

Mikel

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Try it and see? Worst case it grenades and you have to swap in a P-pump, or is that not an easy swap?

Since my disposable income has been drastically reduced, I would prefer to take advantage of other people's experiences.
 

larboc

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Since my disposable income has been drastically reduced, I would prefer to take advantage of other people's experiences.

Sorry, I just assumed everyone had a plastic tote of used power steering pumps they've been carting around for 10 year and never used.
 

Mikel

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Sorry, I just assumed everyone had a plastic tote of used power steering pumps they've been carting around for 10 year and never used.

Normally that would be the case, but the standard Saginaw pumps that I have don't fit my pump brackets.
 

JR4X

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What is the hydroboost off of? There was a "Dumptruck" P-pump that sounds like what you're describing, came on gas engine 2 and 3 ton trucks in the 60's and 70's. Jesse Haines had scrounged one up and put it on the rig my buddy Mitch bought. When it got weak we found out it was discontinued and you couldn't get them any more. Ended up swapping to a CBR pump. But all the same stuff that you do to a p-pump worked on that thing, IE: porting for flow and either shimming - stretching - changing the spring for more pressure output. The GM hydroboost is meant for a 1200 psi pump but I have ran 1500 psi to the stock GM HB units and jeep Saginaw boxes with no problem. I wouldn't hesitate to crank it to 1500, the HB and steering box won't be phased by it. Shortens the life of the pump but you already have it and it will let you know if 1500 psi is the ticket or not.
 

Mikel

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It's from a 76 Cadillac Eldorado. Thank you.
 
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Mikel

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So I sent the other pump to about 1,500 PSI and both the steering on the brakes work well, except I still need to purge the air out of the system. The only thing is that the brake pedal is still a little stiff for my taste. I suspect it's because of my my pedal geometry which I can't change without butchering my firewall. Max braking power is not a problem.

Looking at how a hydroboost works, it seems to me that if I reduce the preload on the spring behind the pressure regulator valve, it will cause the brakes to actuate at a lower pedal load. Does this make sense? Thank you.

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Provience

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yes, but i would try a little bit at a time because a little goes a long ways.

it seems to me that if it was expecting to be used with a larger pump than what you've got, that more preload spring would be required to make sure it is able to cut off pressure when needed as well as resist self application of the brakes.

springs are pretty cheap if you can measure what size and rate it is currently and then pick up a couple that are lower rate to see what works.

if your pedal remains stiff, i think you should consider a master cylinder that is 1/32-1/16" or possibly even 1/8" smaller
 
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