power rack operating pressure range

Does anybody know what the operating pressure is for 80 to 85 T-Bird power rack. That is the unit that is in my project and was wondering if it is compatible with the GM pump as I have read (from a tread on this site)that I may need to reduce the pump pressure if the steering is a little too sensitive etc. Haven't fired it up yet, just want to be prepared.


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I believe most Mustang II power rack units operate a 2 gallons per minute and most GM power steering pumps flow at 3 gallons per minute. I found a couple of solutions in Old Dog Street Rods catalog. Detroit speed makes a correction fitting...part number DSE 091401 on page 81. And Billet Specialties makes a control valve....part number BIL RP1300 on page 81 as well. Hope that helps.

Dave

GPM is flow rate, not pressure. The flow rate has no effect on steering assist (unless you run out of fluid). The pressure is specified in pounds per square inch. There are adjustable needle valves that you can put in line in your PS high pressure hose to dial in the pressure (and level of assist) that you want. There's no real mystery to this, it's really a direct relationship (steering assist is just piston area times pressure). GM has a speed sensitive steering option that simply puts a pulsewidth modulated valve on the output fitting of the normal Saginaw pump. The computer reads road speed and varies pressure (and steering assist) to match. An analog valve would do the same thing.

What GM pump are you using? If it is the old style you can save some money by just cliping the pressure relief spring in the pump body. cut off one to two coils and try it. Kinda messy but 0 money. John

Then...bump. LOL's. Where can the two of us locate these adjustable needle valves? Part number? The place I got my suspension/rack unit said he had a kit (shims) to use with the GM power steering pump that would reduce the pressure. Will that work in place of the adjustable needle valve. The problem I have....I'm not sure how to find out what the pressure is....in the relation to the number of shims I place.

The truth is....your correct. I didnt read his post correctly. But....wouldnt an increase in orfice size decrease pressure? I'm just curious as the parts I was talking about look like they do nothing more than change flow rate by changing pressure. I'm not being criticle. Just being curious.

Dave

Thanks Joe!!!

With your help I found what I think the two of us were looking for. Heidts sells one (part # PS-101) as well as many others on the net. Just do a search for power steering adjustable needle valve.

55 El Camino is right if your running an early model GM pump. I'm running an LS1 which I'm told also has the ability to modify pressure with shims. I was just looking for something quick and easy. I like the idea of the adjustable valve because I might not like how the steering feels. Just a quick change of the knob and....

I feel real foolish now.

Dave

Thanks for the input. I did some more searching and found another thread on this site that said that the later T bird racks were more compatible with the saginaw pumps and did not have the trouble that the earlier Mustang 11 racks experienced. That is why I was asking what the operating pressure was for the T-bird rack as apparently the pressure for the Mustang 11 racks is around 800 to 900 and the saginaw pumps put out up to 1200psi. What I will do is run it and if there is a problem do one of the fixes as mentioned.

In reality, flow rate and pressure are related (just like voltage and current) so that for a fixed line size changing one usually changes the other. Raising pressure through a line (assuming there are no other limiting restrictions elsewhere) will raise flow rate.

As long as you are using the t bird rack with the g.m. saginaw pump, no change in either is required. I run the exact setup on my coupe, and have set up numerous customer cars with this combo.,and have never had an issue!

I am using the late (90) mustang rack does the gm pump (2003 yukon) have the correct pressure or do I need to reduce the pressure?

Thanks

your rack is the mustang with the triangle-shaped input shaft? It should be compatible with the late model remote reservoir g.m. power steering pump

The shaft is round 3/4"X 36 spline. That is what the vibration u-joint I bought. It was off a 1990 Mustang with 5.0 engine.

OkAY, I'll do something more people should try!I admit, I've never used a 90's mustang rack so I'll admit I DON'T KNOW!! Are you using this rack on a mustangII setup?

Yes this is on a Mustang II setup. I was under the impression that it is what I needed. It bolted on correctly and I am using the stock MII tie rod ends.

Not a mustang guy, but the info should be available here, or through other sources, to tell you what that rack used as a factory pressure. Generally Mustang racks are around 1000 psi, and gm pumps 1250 to 1350, so you may have a problem. But it is not serious. Borgeson sells the shim kit, (under $20)with a guide to how many shims to add to reduce pressure to a certain amount. Depending on your personal preference, you may reduce it below the original specs to make steering a little firmer. More info in the Wiki - Cavalier rack install.