Power Steering Mod - Fell in love with my Mark 4

[Chris Mann]

I just finished a Mark 4 with a 347 after I totaled my Mark 3 (306) last September. One thing I loved about the Mk3 was the manual steering at speed, it was like a guided missile. I chose to put in a stock power steering rack in this one and lost all road feel, confidence in and out of corners and overall driving satisfaction in order to gain some low speed steering ease. So I had the option of a Heidts valve or cutting the internal pressure regulating spring in the pump. The Heidts valve would give adjustability but would cost $100 plus to put in with modified hoses, etc. So I decided to open up the pump and cut the spring.



I pulled the return line and caught about 6 oz of fluid in a cup. I put a cap on the line to avoid more spills. Then remove the pressure hose with a 5/8 wrench. The mod could have been easily done in situ but not knowing the exact lay out I pulled the assembly.



Pull the pressure line fitting (13/16). That exposed the cylinder and the spring is behind that.


I pulled the spring with a magnet and cut it to about 1 7/16 inch.


I ground the cut end smooth and put it back together with the cut side towards the outside.

My test drive was wonderful: easy to steer, great road feel and confidence in corners. Not quite a guided missile but something I could fall in love with and I did.

The new 347 is great with the car but felt a little squirrelly. Now it is great. So maybe if you think your car is overpowered maybe it is just oversteered.

[SCracer]

OK, you've convinced me, i'm going to do this.

Nicely documented...great contribution to the forum!

thanks!

[Gregg W]

Very well done Chris. That is one heck of a camera. Gregg

[Greg_M]

Chris,
Good writeup. I performed this mod a few years ago based on others experience. Can't say how much it reduced the assist since I never drove it stock but I agree with you that it feels good and there is no situation where quick steering input "gets ahead of" the pump in any circumstance in 14,000 miles.

Thanks for documenting this. I hope you don't mind that I used your photo on the buildsite

Greg

[ZoaFan08]

This couldn't have been posted at a better time! After going for a ride in Eddies roadster he told me about this mod and I was researching it, looks like a very simple mod to do! Thanks!

[DMW]

I just did this last night, leaving the PS pump on the car. It couldn't have been easier. Thanks for the documentation. My initial driving impressions are that the steerign is still nice and light at very low speeds but feels firmer on the highway. It's not too drastic a change but definitely in the right direction. Without this mod, the PS is just way too light.

[cobradawg]

I've been looking at this mod for a long time. May I ask which pump that is, and which rack did you use? I don't have AC so how should I mount the pump on a 302? Thanks for posting those pictures, they are very helpful.

[Greg_M]

That looks like the stock Fox pump.

Dawg, I added PS to the late Don Voorhis's car in a long day. You will need a power rack (Autozone is fine), a reverse water pump (for serpantine setup), a Fox PS pump, a March PS mounting bracket, and a belt. You can an use the stock hoses and make extensions or just do a custom hose configuration. See pics here from Don's car:

Don's Mk3.1 FFR Cobra Build Site - Power Steering Added - Worldisround photo
Don's Mk3.1 FFR Cobra Build Site - Power Steering Parts List - Worldisround photo

and one of Don using it. Rest in peace Buddy.
Don's Mk3.1 FFR Cobra Build Site - Don Driving On A Cool Fall Day - Worldisround photo

Greg

[CraigS]

You can experiment w/ cutting a little more if you want. If you go too far,just find appropriate diameter washers to shim it back again.

[AC Bill]

That lack of steering feedback, and road feel with PS, was one of the main reasons I didn't go with it.
This mod is certainly a good way to save $$, but wonder if a Heidts valve could be the best way to go in the long run. You could then tune the steering for the type of driving your doing. IE track, or street. Might be nice to be able to adjust it for different drivers as well, in case the Wife likes it a little easier.

[Useless]

I would think about putting a simple cooler on the return line really made my car a lot nicer to drive with the power steering so i know the feeling ---dave

[CraigS]

I don't know why but I didn't like the Heidts valve on mine. When I got the steering effort the way I liked it at speed, I sometimes got a lack of assist in a parking lot while manuevering w/ the engine at very near idle. My Heidts valve has been in the cabinet for 3 yrs now. BTW, send me an email if you want to try it for $20.

[LuisL]

Could this be done on a Modular motor style steering pump? That's what I have so I have to ask...

Thanks


Sent from my Autoguide iPhone app

[DMW]

After driving on the interstate for a few hours yesterday, I'd like to actually make mine a firmer. Quesiton: How short can the spring be? I was thinking of cutting off one more rotation of the spring but don't want to overdo it.

[Greg_M]

Dave,
Cut one more coil and let us know if: it provides more feedback at speed: and you don't get ahead of the steering at low rpm. I have a spare spring if you cut too far

Greg

[DMW]

I cut the spring about 2/16th from the first cut so now I am at 1 5/16ths and it is still functioning! The steering did firm up a little more. Before cutting the spring, I could do a u-turn with one pinky. Now it is about a 2 finger job so that's about right.

Now, on to the issue with bump steer...

[NiceGuyEddie]

ROCK AND ROLL!

it truly cost nothing, and the return is amazing!

best free mod in the book. and you did the right thing by making a "flat part" on the cut end of the spring.

best writeup i've seen, many will benefit from this.

[CraigS]

I am glad it is working out for you and i hope you inspire others to do the same thing. I strongly believe we should do what we can to make these cars drive normally. A h-ll of a lot faster, but just as easy to control as our daily drivers. I don't think it's good to need 5 minutes of acclimitization every time one hops in his FFR. Good work and nice pics.
LuisL-look around on your mod motor PS pump for a similiar cap/plug. Many pumps have the same setup (my 99 Explorer pump does) but I am not sure about yours.

[Greg_M]

Thats right. Pumps using a remote reservoir have the spring under a cap not in the line fitting.

Greg