All - I'm toying with the idea of 'upgrading' my old truck to use a Toyota steering box. The stock box has a fair bit of wear - not excessive, but enough that it's annoying. I've considered rebuilding it, but for that much effort and hassle, I'd just as soon swap it out. This is more of a 'dark side' truck than a stocker anyway.

With the Toytoa box, I may stick with manual, but also considering a power steering upgrade as well.

I have a 5.0/302 Ford in my '54 F100 right now, and it has provisions for the original PS pump (currently removed & shorter belt fitted). However, since it's out of a Mustang, that pump is meant for rack-&-pinion steering, which I believe is much higher pressure than a recirculating ball box would normally use.

Two questions:

1 - Is there a pressure reducer that will work, or a pressure reducer valve from a different Ford application that will bolt into the power steering pump so it will work with the Toyota power box?

2 - Is there a power steering pump from a different non-rack Ford application that will bolt to the stock brackets and uses the same serpentine (K6?) belt system?

I have made no decisions yet, but the Toyota box seems the most obvious and straight-forward option. I'd be interested in hearing other options for upgrade - manual or power.

TIA

 

A quick Google & eBay research looks like 79-90 Crown Vic or 79-91 Grand Marquis used the 5.0, serpentine, same physical dimension pump. The question is, is it in the control valve, or is the pump internally different? Anyone know? My gut says it's in the control valve...

 

A lot of factors determine how much pressure any one pump is set at - handling, steering type (racks and power assist typically require less pressure than recirculating ball), tire size, etc. Most pumps are capable of more pressure than they are set to deliver. Adjustments to the pressure relief valve are made either by spring tension or shimming the spring length to increase/decrease the spring tension. Some pumps utilize a throttling valve, others may employ higher flow rates. In other words, it can be a crapshoot unless you have a lot of experience or charts to go by. From what I've read the sellers of the systems you describe typically recommend using a GM Saginaw pump as it normally is set to supply lower pressure than the typical Ford pump. The kits I've seen include a shim or two to adjust the Saginaw pump's output, if necessary (basically remove the pressure line from the rear of the pump then the fitting the line attaches to and insert a washer beneath the fitting, thereby reducing the pressure) Also available are adjustable flow valves, however they can be a little pricey and require some additional plumbing.

The control valve simply opens and closes allowing pressure to be applied (most cases.) Many racks place pressure on both sides of their piston and the control valve allows the pressure to drop instead of increase. The reasoning is this way full power is instantly available at all times and response rate is enhanced.

 

As an ex-heavy equipment mechanic and reasonably well versed in hydraulics, I get all of this. I was merely calling it a control valve because that's the nomenclature in the parts diagrams I found online. Pressure relief valves come in two flavors: 1 - regulating valves and blow-off valves. The former are often called control valves because they regulate pressure. The latter are normally just called relief valves because they relieve excess pressure.

Regardless, you are correct, pressure in these simple systems is controlled via spring pressure. The "control valve" depicted in the diagrams seats on a spring...

Most Saginaw pumps put out between 1000-1300 psi, with a few heavier (truck) applications putting out a little more. The Ford pumps for R&P put out anywhere from 700-900psi (so I had it backwards in my original post).


Increasing spring pressure by shimming a spring, generally increases pressure.

All I've seen online are adjustable valves that are not really true flow control valves, but they relieve pressure by bypassing some of the pump output back to the return line. So, while some flow is lost, it is not a true flow control valve.

Understood. See above for terminology confusion. Many systems provide pressure on both sides, it is precisely the pressure differential (drop on one side) when you turn the wheels that causes the pump to 'kick in' and assist in an attempt to equalize pressure on both sides. In fact, most steering operates on the basis of equal pressure on both sides as 'neutral' (ie - steering aligned with steering wheel input).


So, since you seem to know a little bit. I'll restate my question:

Can I simply use the spring & valve from pump originally installed on a recirculating ball type car (Crown Vic, Grand Marquis) into my pump that was originally a R&P setup? Or is there enough flow difference in the internals of the pump to require different georotors and pump components? (ie - do I need the whole pump?)

In a perfect world, each pump would be tailor made for each application. OEMs, however, operate on greatest commonality of parts concept, so many parts are 'tuned' to the application instead of being tailor made. Since the physical appearance of the Crown Vic/Grand Marquis pump appears to be identical to the Mustang pump, is it safe to assume this is a case of function following form - internals tuned for application instead of tailor made pumps for application? If so, what is different? Just the spring/valve? Or the entire pump?

 

Shimming is done at the nut on a Saginaw pump, backing the nut away from the pump and thereby reducing spring tension. Agreed that shimming a spring would normally increase its tension resulting in higher line pressure.

Agreed, the 'flow control' valves are really pressure reducing valves, diverting excess pressure back to the reservoir. I was merely using their terminology as shown in the catalog to avoid confusion. Their feature is that they are easily adjustable compared to shimming, exchanging springs, etc. This was just answer to your question #1.

I was just tossing in a little extra info regarding the control valves on a rack. Most peeps don't realize how one rack can feel vastly different from another. Of course we could include info on PWM valves, etc. but it's doubtful anyone on this forum would be using one.

Also agreed that most OE pumps run 'typical' pressures rather than wide variances. But there are always exceptions, looking at the parts list for the pump in a '91 CV there are some differences between a police pkg. and a standard CV. However the relief valve spring doesn't show a difference nor does the pump housing, rotor, etc. So I suppose the difference lies in the relief valve itself. Unfortunately individual parts for it are not listed.

So, we're back to square #1. We know racks require less pressure than recirc' ball gears, we know the catalogs for the P/S kits recommend Saginaw due to its lower pressure. We know there is an easy way to adjust pressure on Saginaw but not as easy as an add-on regulator. My best guess is to mount a pump for a rack and see how it drives. Then you can decide if you want to adapt a Saginaw pump or install an inline regulator.

 

Well, I can easily mount a Crown Vic/Grand Marquis or even Ranger pump - all use the same pump body, so should bolt to my brackets. That way I'd have a recirculating type pump with a slightly higher pressure as a starting point, rather than the RP pump...

Thanks - it's good to think out loud sometimes with someone who can think with you!