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Power Steering Rack Installation Question

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Power Steering Rack Installation Question Empty Power Steering Rack Installation Question

Post by Jeff Richards on Thu Feb 08, 2018 9:37 pm

Hi,

I'm converting from manual to power steering in my 5000. The build manual talks about adding 3/4" spacers between the rack and frame cross member when installing a power rack. Anyone know why?
Jeff Richards
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Post by Derson on Wed Dec 26, 2018 11:42 am

Jeff,
I'm trying to replace my manual steering to power like you were last Feb. I came across the same note in the manual. Did you ever resolve the question?
Thanks.

Derson

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Post by johnhappley on Wed May 22, 2019 3:03 pm

I'm replacing my manual rack and pinion with power steering. The manual R & P has three
attachment bushings. The outermost are about 15 3/4" center to center. Most R & Ps are 15 1/2 with just two bushings. I can buy offset bushings to handle the 1/4" difference.

My question is what did my three bushing manual R & P come off of? I'd search for a power version if I knew where it came from. Otherwise, I'll go with a two bushing power rack.

Thanks,
John

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Post by Derson on Wed May 22, 2019 6:03 pm

I think I've discovered why the 3/4" spacers are needed. The spacers move the rack and pinion forward enough so you can get the belt(s) between the crank pully and the hydraulic line coming out of the rack.

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Post by Hotrod on Wed May 22, 2019 6:16 pm

I believe the 3 bolt units are original Mustang II.  The later Fox body Mustangs lost the extra boss on the inside.

I'm at work right now and answering on my phone. I'll try to comment more after I get home.
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Post by Hotrod on Wed May 22, 2019 10:36 pm

According to the info I have, the MII racks are 16" center to center.

The Fox units are 15.5" C to C.

I recommend you use a Fox body unit.  These were used on Mustangs and Thunderbirds in the 1980's and into the 90's.  They can tolerate higher pump pressures than the MII spec units.  To use a Fox rack on a MII spacing you will need the offset bushings.

I don't know what engine you're using, but if it's a Chevy, the common GM pumps put up too much pressure for the MII racks.  I know from experience with my 46 Coupe.  The high line pressure results in way too much power assist and makes the steering very sensitive with little road feel.  Combine this with the fast 2.5 turns lock to lock steering ratio and you have a dangerous combo.

Even if you are using a Ford engine and pump, you may still have too much pressure.  The MII/Pinto platform was very light weight and Ford used a low pressure system.  I think it was only around 600 or 700 PSI.  A pump off of a heavier Ford car will most likely have a much higher pressure calibration than a MII pump.

The Fox rack was designed for a higher pressure from the start and is said to tolerate the GM pumps much better.  But, this doesn't mean that you can't still have an overboost situation.  The front end on a Sebring probably only weighs about 1100 LBs  and I'm sure that's a lot less than the front end of a T-Bird or Fox Mustang.

If you do have overboost, the street rod industry has a couple of solutions available.  There are recalibration kits for GM pumps that lower the pressure, but you need to know how much you want to lower it.  Considering that the pump will have to come off for every adjustment and how difficult it will probably be to remove the pump on a Sebring, you might want to consider another route.

The better solution (IMO), is an adjustable bypass valve made by Heidts (street rod supplier).  It plumbs into the hoses between the pump and rack and allows you raise or lower the line pressure just by turning a nut.  It can be mounted anywhere you have room for access and can get to with the hoses. Very handy and is the solution I used to solve my overboost problem.  BTW - My 46 coupe weighs about 2000LBs on the front end and still suffered from too much assist.  Of course, main downside to the Heidts valve is that it's the most expensive fix.  

You will need a hose kit, too.  You can usually have hydraulic hoses made locally, but my experience is that these tend to be very stiff as they are made using hose with a very high pressure rating. Heidts also sells a plumbing kit with -6 stainless braided teflon hose that you can make up yourself.  Way more flexible and easier to route.  The kit is available for the in-line valve or without.

One more issue you will encounter.  The splines on the manual rack are 9/16-26 where the steering shaft attaches while the power racks are 3/4-36.  If go with a mid 90's era sn-95 rack, they have an unusual triangle shaped input shaft.  The good news is that aftermarket steering u-joints are available to fit all of these input shafts.  The bad new is that they are not at all cheap. Stick with Borgeson, Flaming River or Sweets for these joints.  Good quality stuff that I will bet my life on (and have).

Sorry for the long post.
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Post by johnhappley on Sun Jan 19, 2020 2:58 pm

I need to start writing this manual to power steering conversion before I forget the details. Hotrod helped me out a lot via private messages but I can't publish all of them as we worked through the issues [too long]. The reader now gets the benefit of avoiding mistakes, floundering, and false starts. So here are the issues and I'll keep adding details as I go through my receipts.

This installation guide is for a Ford 302 without air conditioning. I had a double crank pulley to work with that was unused [outer groove]. The inner vee groove handled the water pump and alternator on one belt. So the outer groove was the logical choice but I have seen engines using the inner vee groove for the power steering pump. This leads into issue 1. I'll try not to swear too much...

1) I purchased an aluminum billet pump bracket from ??? and pulley [4" ?]. But it was designed for the INNER crank pulley groove. Do they tell you this "NO". So most of the long allen bolts that mount into the water pump and spacers are too short. I had to order longer bolts [?"] and added spacers [see photo] until the PS pump pulley lined up with the outer groove of the crank pulley. Which leads to issue 2.

2) I ordered a PS pump from [?] which is the 80s Ford compact style with the tall reservoir stack. Well it DOES mount to the bracket BUT does not have a rear mount [to the head]. Sure enough, in the vague fine print the bracket people suggest the 70s Ford model which is much bigger and has a rear mount where the high pressure line exits. So I do an exchange. I then press on the aluminum pulley and mount the big mother in the bracket. Funny thing, it feels very rigid as is. Why do I need the rear bracket to the head??? The rear high pressure fitting just misses the exhaust manifold by 1/8" [crap]. Guess I should have went with the 80s compact pump after all. Too late.

3) The PS pump and rack & pinion [R&P] have fittings intended for hard lines with flares. You are now warned. I decided to make my own FLEX type because of routing problems. For the high pressure line DO NOT use the the stainless wire mesh hose. They are absolutely miserable to put AN-6 fittings on. And they don't flex much. Get the nylon mesh hose instead. They will handle the line pressure just fine and save you a ton of grief. I spent hours researching hydraulic fittings. You need kind of a special fitting to start off at the rear of the pump with AN-6. Then its a AN-6 90, a AN-6 union, a AN-6 90, the armored hose [with AN-6 fittings on the ends], and finally a fitting into the R&P. The low pressure side is much simpler. Again you you need kind of a special fitting exiting the R&P [remember the warning above]. Then just use 3/8" urethane/rubber hose to connect to the PS pump. Put a trans filter in the line. Fill the pump with Dexron III/Mercon transmission fluid [+1 quart]. Special fittings mentioned above sometimes need a small O ring inside to seal with because you don't have a flare to mate with. Mine don't leak.

4) My manual R&P of 4 turns lock to lock had 3 mounts to the crossmember [see photo above]. I don't know where it came from and never found a 3 mount power R&P. Don't let it bother you, you'll get over it. You will have to buy OFFSET urethane bushing mounts with washers. And yes you do need to space the R&P 1/2" to 3/4" away from the crossmember. Otherwise it hits the crossmember where the boots attach. Attach the tie rods and adjust for toe-in [threads were the same]. Make sure the steering wheel is centered [see below]. The Ford Fox Body R&P [not TRW] from Autozone is made by ? and is both inexpensive and high quality. The castings look so new, I doubt it is rebuilt. The splined R&P input shaft is larger on the power version and is a tight fit past the the lower radiator inlet. Power rack is 2 1/4 turns lock to lock [sport version]. When jacked up and engine running, turn the tires/steering wheel lock to lock several times to get the air out [self-bleeding].

5) After much discussion with Hotrod, he convinced me to go with a 3/4 DD [double D] steering shaft [cut-to-fit]. I had a 1" shaft with welded U joints for the manual R&P. Its now in a landfill. So each 3/4" U joint has a female spline on one end and a female DD on the other. Bolts allow for minor adjustment and hold in place. Make sure the threaded tie rods are centered in the R&P [maybe]. Mark the R&P input spline/casing and then center the steering wheel. Now you can mate the steering shaft U joint to the spline input shaft. Now here is the catch, the R&P is not exactly centered on the crossmember. But the tie rod shafts need to be centered [relative to the tie rod ends, makes sense] and so does the steering wheel and so do the tires [if you want to drive in a straight line :0} ]. So its possible that my piston in the R&P is not exactly centered in the casting [tube]. Let me know if I am in error here. Toe-in is 1/8 to 3/8" on centers of tire tread which must be on the ground [no jacks].

I'll work on this later, Marilou wants something.

This is getting long winded. I'll put a bill of material on a separate posting. I think this power steering conversion is worth the loss of a few horsepower. My MX Sebring was not fun to turn. Marilou wouldn't drive it. Maybe my imaginary girlfriend Bertha would. I also put QA1 dampening adjustable shocks on the front [not coilovers] because I like the current height. I set them to a soft #2 setting since the car is so light. I am currently struggling with a front sway bar installation too which I will publish later. I wish I had got to the car before the last HACK did. Reminds me of some beautiful women I've known. Just don't look under the hood. And this Healey does have a body on her.


Last edited by johnhappley on Sun Jan 19, 2020 8:36 pm; edited 1 time in total
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Post by Jeff Richards on Sun Jan 19, 2020 4:55 pm

GM type II pump with a reservoir on the inner fender worked great for me. Built my own hoses- stainless braid for the pressure lines.[You must be registered and logged in to see this link.][/url]
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