Mark IV Power Brake Booster - Steering Clearance issue

[mrglaeser]

I been working on modification to use a Fox body power brake booster. I cut the frame and fit Whitby's frame mod. I dye grinded the pushrod hole to fit big rubber boot. I got a spacer from http://www.replicaparts.com/. But I could not get the booster to sit flush with the firewall. When I looked it was hung up on the steering.

I then proceeded to remove the Booster, all the steering components, and the pedal box. I wanted to move the pivot from the exterior to interior of the firewall as I saw on a different post. I had to clearance the pedal box to do this. Finished the clearancing and reinstalled the pedal box and steering components. This cleared up 80% of the gap... but not all. The booster still makes contact with the steering components and will not go flush on the firewall. See pics.

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-rq8zthg/0/148fc7cb/XL/20230614_182542-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-rq8zthg/A)

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-f6w5rVd/0/d7cd44de/XL/20230614_182554-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-f6w5rVd/A)

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-WShNWRB/0/cb608f7d/XL/20230614_182607-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-WShNWRB/A)

I think I could get the clearance if I cut the linkage by about 1 inch that goes from the firewall to the steering rack, but I'm worried the angle might cause issues with movement of the steering system.

Another option would be to try and find a booster with a smaller overall diameter. I'm not sure where to start, anyone know of a booster with the same bolt pattern but more compact?

Anyway any suggestions would be greatly appreciated. If it matters I have the FF5 power steering kit.

[michael everson]

In every build I have done, that joint is right against the bearing. The rod should not protrude into the joint at all. You need to reposition everything until that joint is on the right place.
Mike

[DW66]

185853185852 Exactly what Mike said here are a couple of pictures. U-Joint very close to the firewall bearing.

[mrglaeser]

Thanks Mike for for the response and DW66 for the photos. I'll see if I can get a similar setup going. I think I did have it that way a couple of months ago and moved it thinking there 'should' be some space between the pivot and steering joint.

[mrglaeser]

Well I tried moving the steering components as suggested and it didn't work. You can see in the pic the joint is as close to the pivot as possible. However looking at DW66 I am noticing his booster looks a different than mine.

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-kqNZgP2/0/8e344c26/XL/20230615_222415-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-kqNZgP2/A)

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-FN2TvWp/0/bea8d1b5/XL/20230615_222350-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-FN2TvWp/A)

Looking through my order history I purchased:
Cardone Remanufactured Power Brake Boosters 5473155

Apparently this is for a 1993 only Mustang Cobra or Cobra R

There are 2 others listed for 1987 - 1993
Cardone Remanufactured Power Brake Boosters 5474000 nd 54-73207 (I think the second one is what I want)

So.... I guess I'll see if I can find one of those (summit says will ship Sept 12)

[Norm B]

Try RockAuto. They usually have better prices than everyone else

[michael everson]

Autozone stocks brand new ones.
Mike

[DW66]

That explains it. I know the Cobra booster is bigger for a fact. I don't have the part # of mine in front of me but I know it was for a regular Foxbody Mustang not a Cobra. I would be pretty confident thats the problem. I am using a Cobra master cylinder. FYI.

[mrglaeser]

Autozone stocks brand new ones.
Mike

Thanks Mike. You were. Correct i found an autozone with one on hand but that store is 70 mile round trip.

Luckily though OReilly's had one in the local warehouse so i picked it up this evening at the store a couple miles away. It is much smaller than the one I was working with before.

Now for the fun part of trying to get the spacer off the other one. It took a little persuading to get on.

[michael everson]

Drill the holes out to 1/2 inch on the spacer.
Mike

[mrglaeser]

Well just thought I'd finish the thread. The standard 87-93 v8 brake booster with the 93 cobra MC seem to work great. The 93 Cobra booster interferes with the steering.

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-8kmzhKf/0/4af12371/X2/20230617_144037-X2.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-8kmzhKf/A)

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-VGLFFRj/0/4f89fe2b/XL/20230617_144026-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-VGLFFRj/A)

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-HDKHZS7/0/e1a028a4/XL/20230617_144023-XL.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-HDKHZS7/A)

Now to mount the proportioning valve and start running the brake lines

https://photos.smugmug.com/Home/9999-Factory-Five-Roadster/i-SzhXHqn/0/af5ca0a0/X2/20230619_191849-X2.jpg (https://mattglaeser.smugmug.com/Home/9999-Factory-Five-Roadster/i-SzhXHqn/A)

Thanks everyone for the help

[Norm B]

Great! Now all you need is a stainless steel pet bowl for the relief area so the splash panel (elephant ear ) can fit.

Norm

[CraigS]

STOP. Proportioning valve? What are you planning and what are you using it for?

[mrglaeser]

STOP. Proportioning valve? What are you planning and what are you using it for?

The plan is to set the brake bias between the front and rear brakes. I though this was a common device to use? They are installed on most factory vehicles no? The design as I understand it is to keep the rear brakes from locking up before the front brakes. The instructions that came with the part I purchase have pretty simple setup. A few test runs at increasing speed, reduce/increase pressure to the back brakes until the lock at the desired timing.

https://www.summitracing.com/parts/WIL-260-12627

[mrglaeser]

One thing to note I'm using the Fox body pedal box so there is no balance bar or adjustment there. Also I have Wilwoods front and back so I didn't think using a stock valve from a Fox body would work as well.