I'm in the middle of thinking about power steering options for my 2 240s, and I'm wondering about interchangeability between years and models. Currently the Smurf needs a new rack, and I'm thinking about swapping the one from the YROG over to it. Couple questions:
-are there problems with keeping the '75 pump and running the '79 rack with it, so its a straight swap?
-once the YROG is without a rack, I'm thinking of running a later 240 rack (as per Matt's suggestion). Again, is there any issue with keeping the earlier pump and running the later style rack?

After looking on FCP, it would appear they sell a late model rack...Matt, would this be the one you were referring to?
http://www.fcpgroton.com/product-exec/p ... ory_id/173

I was on one of Anthony Hyde's pages:
http://people.physics.anu.edu.au/~amh11 ... rs_trw.htm
He lists the later rack '88+ as lighter, and Matt, you said it had a better feel as well?

Thoughts?

If my P/S set-up is any indication I would say there would be no problems mixing and matching. All power steering pumps do the same thing, the only difference is what the pressure is set at and the volume. Higher pressure will give easier steering and less road feel, the opposite for lower pressure. As for flow or volume a rack or P/S box will only use up to a certain amount so too high a volume is not a problem but too low a volume will result in the pump being unable to keep up to fast steering input (rapid lock to lock).

The 740 pump (may have been used on some 200 series I am not sure), is a great little remote unit that would bolt right on and keep the engine bay looking clean.

The 740 pumps and 240 pumps are all compatible except maybe the early ZF 75-77 240 stuff, which I don't know a ton about.

I'd echo what Ian said mostly...a PS pump is a PS pump for the most part, with or without out hooptie trademark ford noises with or without leaking or self-destruction regardless of brand.

Lowering the pressure isn't always a good idea for better steering or road feel. There is valve in the PS pump (in basically all PS pumps) that keeps the pressure supplied to the rack constant as the demand for volume changes based on how much torque is applied to the steering shaft. The input torque is used to open the directional valve in the rack and increase the fluid volume and thus the force put on the pistons in the rack. How well the whole PS system works together from the steering wheel to the tie rod ends that translate what your hand does to what the wheel on the ground does is a little more involved.

I would venture to state that simply decreasing the total operating pressure of the PS pump/high pressure hose is more along the lines of "band-aid" than a good overall solution to feel problems or desired assist. While you might decrease the total assist available, you might also make it so that the input torque on the steering shaft increases for the same driving. The idea being that you are nearer to full assist the whole time you are driving....you might be working harder without much benefit in actual precision of the parts themselves or increases in "road feel." By changing the shims or springs a bunch in the line pressure regulator valve in the pump you might also exceed the travel range of what the piston in the valve is designed to do...whoever made the OE valve made it with a certain pressure with a maximum volume demand in mind. If you move the valve outside if its range, you might wind up with uneven line pressure...no idea what would happen in that case...could be little or nothing or really rather ugly.

The 80 and older PS on a 240 feels like a video game to me. 81 and newer they got a lot better when they are in good repair. My cop car had a brand new ZF rack put in it shortly before I got it and it drove great, though the late cam or TRW aren't bad either when they are new. To convert from MS to PS you need the whole linkage and such from the firewall forward from my memory. Running the later rack with the ZF pump on the B20 shouldn't be a huge deal I wouldn't think, though somewhere there might be a published spec for the operating pressure of the pumps...maybe even a max volume (min volume would be ~zero of course). I'd bet they are the same, but I wouldn't ASSume either.

Racks seem to give up the ghost in cold weather cars a whole lot more than warm weather ones for whatever reason as far as leaking or seal issues or directional valve issues go. In most cali cars that have fluid they seem to last forever. Synthetic fluid in a fresh rack seems to keep them alive in the cold. Strangely, that is also where I notice the most difference between synthetic and cheap ATF in AWs too in just people's bone stock DD cars. They shift a whole lot better stone cold with the better fluid and the PS pump moans a whole lot less.
The wear items and quality of the parts in the ZFs used ~81-86 seem to be best from what I can tell. The seals do go in them though.
I went from manual to power steer recently in the red 242DL. Manual steering is horrible. PS is not bad in a 240 when it is working right and I love it. I want to drive the car to the gym laughing like a lunatic with the car sideways, not be at the gym already with a grimace fighting the car. If I had an Amazon it would have PS even...though the ratio of the Amazon isn't bad like the 240 manual rack...I just like PS a lot even with the 140 power box.

Thanks Ian and James for your responses. Greatly appreciated.

The Smurf did have PS originally, I've just been running without it for the past while after my last rack died. I'll agree that I hate driving without PS on this car. While I haven't tried it with my narrower winter tires, I can only imagine it still sucking. I have no idea how in an emergency situtation I'd be able to steer fast enough with it as is. I do hate the feel of the rack on the YROG as well though...its just dead. I like your description James...a video game. But if its on my winter beater, feel isn't that much of a concern to me.

My plan then is to swap the PS rack from the '79 to the '75, keep the stock B20 pump, and see how that goes. As suggested, I'd like to find out what the volume and pressure for the respective racks would be, but my manuals say nothing. Craig, would you mind checking your green books quick to see if they say anything? From there, I'll be searching out a later rack for the YROG.

I've checked the Green Manual as requested and found the following. The Smurf (as suspected) as the lower pressure ZF pump that puts out 825 psi at lock and the Saginaw pump in the YROG is higher with pressures between 895 - 995 psi at lock.

You'll be fine.

Perfect. Thanks Craig.