Anyone running a larger power steering pulley to lower power steering boost?

Hi guys, I ran across a reference on another site that mentioned running and 6 inch power steering pump pulley to slow down the pump and thereby increase the steering effort a bit.

Apparently there is a 6 inch pulley from a 1980-1985 (+/-) Ford truck that will fit?

Anyone done this?


I haven’t tried it. But, theoretically, wouldn’t that only help at idle speed? Where or when are you hoping to increase steering effort/feel?

What we really need is to adapt a clutch to the P/S like on A/C units and operate the clutch when needed.
I have thought about a by-pass line from pressure to return line using a valve to throttle fluid.

Hi guys, thanks for the responses.

I believe a larger pulley on the pump will slow down the pump at all speeds making it heavier everywhere.

I was pinging with the Mustang guy and he said the other way to do it is a fluid constrictor .

The cockpit controllable clutch idea is brilliant I had a 69 mustang that I put a unassisted flaming river rack in and it was a total bear in parking garage is in at very low speed, but once you got moving in especially on the highway it was fantastic.

It might be a couple months because I’ve got more pressing issues on this car, but I think I’m gonna give the pulley a try to see how that goes. I’ll write it up and document everything to share here.


Don’t power steering pumps use an integral pressure relief valve to maintain a set pressure? If so, this would only increase steering effort at idle/very low RPM (where you ideally want more assist). At cruising and higher RPMs I would think the pump would still easily reach the PRV pressure even with a larger pulley.

Hi Mike - thanks for the post. Worth nailing this down ahead of time, anyone know for sure?

I know on some other pumps from the same time period you can shim the pump slightly to lower pressure, let me dig that up.

I found this article, sadly they don’t seem to sell a flow restrictor for Ford pumps:

Found them - note these are for Mopars but not sure what, if anything, is applicable to our cars.

Here is the shim mod;

Anyone try an adjustable valve?,14895.html

The speedway adjustable valve is just what I was talking about in post #3 it is used to vary the amount of fluid that will be by-passed. I didn’t know anyone made this, great.

The shims are only used on Saginaw pumps. Thanks for the article.

Yeah that adjustable valve looks like the ticket, the only downside is the additional power steering hoses you’d have running around the engine bay.

Fortunately it is a big engine bay!

Let me see if I can find some pictures of this installed…

Installed on a, um, GM car.

I take it you are trying to get more “road feel”?

You got it - and less steering boost.

There was an article in one of my magazines several years ago, Super Ford, I think, that dealt with this very issue. What the author did was take a couple of “T” fittings and a piece of hose and make a crossover between the high and low pressure power steering lines. In the middle of the crossover he installed a simple rotary valve, similar to an adjustable brake proportioning valve, allowing a portion of the pump pressure to be bled off. He claimed that he was able to adjust it to the exact feel he wanted and that the setup worked great.
Both my Cougars have manual steering so I’ve never had occasion to try it, but it always seemed like a cool idea.

Good morning Jay, hope everyone is well.

Thanks for the post, that is how I am leaning. The Heidts PS-101 Adjustable Power Steering Valve has a rotary adjustment on it that should make dialing in the amount of assist easy.

BTW - I put a manual rack/pinon set up on my 1969 Mustang, bit of a work out when parking but over 10 MPH it was fine and at highway speeds it was just right for my preferences (but I may just be an odd duck, don’t ask my kids for any input on that please).

I have more immediate to-do’s on the Cougar but I think I am going to give this adjustable set up a try.


Yes, I run this pulley, which is actually off a 1975 Mustang II (D5ZZ-3A733-A) to slow the pump down.
I also had a custom lower pulley made (3.75" diameter) to show it down further.

This change was necessary to make the power steering pump last @ 7000 RPM. :slight_smile:

Good morning and thanks for the response.

Don’t think my Cougar will ever see 7,000 rpm unless by very expensive accident, so can I ask how the steering feels with that pulley set up? 50% more effort compared to original? 75% more?

Did you have to modify the pulley or pump nose?

Thanks Vic!