Fox Mustang Power Brake Booster Install


A number of people are aware that the Fox Mustang 2.3L power brake boosters will work in the early Mustangs. I realized in 1996 this swap would work, when I took this same style brake booster from an '80 model Mercury Zephyr to install in my '66 fastback.
I had also installed this same type of booster (taken from a '92 2.3L Mustang), in my friend's blue '65 Mustang that I had adapted the Mk VII rear discs onto.
However, I haven't heard of anyone else or seen anywhere on the web where this style of booster has been sucessfully installed in any of the vintage Mustangs any later than the '66 models --well, until now that is!
Back during the very early months of spring (March,2002), Glen Buzek & I were finalizing the bracket designs to adapt the Mk VII rear discs onto the early Mustangs during that time.
I had obatained the '92 2.3L Mustang booster to install in my friend Steven Haynes' Mustang to work in conjunction with the rear discs.
While I had the booster lying in the shop awaiting to be installed in Steven's '65, I was also simultaneously working on installing this booster onto the pedal support of my '68 Mustang.

A new hole is drilled in the pedal to reinstall the pedal pin lower from its original mounting point (to line up with the booster's curved input rod).

Now the pin is welded in the pedal in its new location.



(Switch on left) p/n BZ-2RQ1-A2 (Switch on right) p/n BZ-2RW899-A2

ABOVE: (Left & Right) These are two styles of Microswitches I've used in lieu of the factory supplied brake switch.

The one on the right is like the one I used in '96 when I had installed the Granada front discs on the '65 Mustang belonging to my friend Steven Haynes. I had mounted it to a bracket I fabricated where the switch was stationary and the pedal made contact with the lever on the switch to turn the brake lights on and off. I had to use this switch because the original MC was the single-pot variety that had a pressure activated switch mounted in the MC itself. 

Once I replaced the single reservoir MC with a dual MC, there was no longer any means of activating the brake lights.

The Microswitch on the left mounts directly to the brake pedal (in the stamped steel bracket at the top of the pedal) and moves with the pedal. The "plunger" makes or breaks the contacts as it comes in contact with the underside of the pedal support.

The three contact terminals on each switch are: NO (Normally Open), NC (Normally Closed, and COM (Common). I wired the switch Normally Closed --(held open at rest).
Basically, this just means that normally the contacts would be closed allowing current flow through the switch and to the brake lights to turn them on. But, with the pedal at rest (not being applied), the contacts are held open so that the lights aren't on all the time. --ONLY when the pedal is stepped upon and the contacts reclose again.

When I installed the 5.0L Fox brake booster in my '68, I used the plunger style Microswitch on the left because I found the clearance above the steering column was very close in trying to use the factory brake light switch. After I changed over to the Mircroswitch, I no longer had any clearance problems.



On the left is a stock, unmodified, brake pedal support. On the right is the modified pedal support. Notice I welded all the original unused holes up solid. This isn't necessary, but I'm a bit of a detail freak about things like this, so I closed all the original holes up. The only two holes in the face of the support now are the ones for the upper two studs on the back of the booster to pass through. 


Here's the 2.3L Fox Mustang power brake booster mounted in place on the '68's pedal support. 



One of the first things you'll notice is there is a factory stamped steel panel (in the master cylinder area) to reinforce this part of the firewall. The '64½-'66 Mustangs do not have this extra reinforcement on their firewalls. I had started welding up all the original holes in the firewall's master cylinder mounting area that were no longer going to be used with the new booster installation.

The large center hole (where the non-power brake master cylinder pushrod passed through the firewall) was made larger for the bellows around the booster's input rod. The oddly-shaped black component mounted on the firewall is a handy item to have when laying out the hole pattern for the booster's studs. This plastic item is found in all Fox Mustangs between the front of the pedal support and the inside of the firewall. I got this one out of my '90 Mustang GT parts car (the same car the 5.0L EFI engine came from that's in this '68 Mustang now). 



This is a shot taken from inside the '68 Mustang. Obviously, everything is gutted inside. This made it a lot easier to work on this installation to say the least. Here, the booster is mounted up to the firewall without the pedal support in place to double check hole spacing and to make sure the booster's studs would pass easily through all four holes in the firewall. 

Pedal support assembly mounted to firewall inside the Mustang.



'84 2.3L Mustang power brake booster mounted to firewall in the '68 Mustang.

Notice that nifty "Cobra" EFI upper intake! --the shape of things to come....

If you'll notice, this aluminum master cylinder's ports exit on the right (engine side) of the MC. Even so, and even with the large EFI intake in place, there will still be plenty of clearance for the brake lines coming out of the MC.

NOTICE: This 2.3L style brake booster is ONLY compatible with vehicles running an automatic transmission, or ones with a cable operated clutch. A JMC-style hydraulic clutch will NOT work with this brake booster, nor will the old style mechanical clutch linkages.

This adaptation in a '67-'68 Mustang performed by Ultrastang Performance™. 


UPDATE: (26/October/2002)

The 5.0L version of the Fox Mustang brake booster WILL work in the '67-'70 Mustang applications! The 5.0L version will also work in the '65-'66s.

This is especially good news for those that have a mechanical clutch linkage or (like me) that have the much better hydraulic clutch setup and that want to have power brakes too, since the 2.3L version brake booster covers up the hole where the mechanical clutch linkage or where the hydraulic clutch master cylinder would go through the firewall so that you can't use either of these clutch setups with the 2.3L booster.

At any rate, this discovery will be a great advancement for the vintage Mustang enthusiast in giving us one more option in the persuit of improvement of these old cars!

Ultrastang Performance™: First on the www to announce that the 2.3L & 5.0L Fox boosters will fit the '67-'70 Mustangs.


DEC. '02/JAN. '03 Photo Update: 2.3L & 5.0L Fox Brake Booster Comparison 

Booster on the left is the 2.3L Fox version and on the right is the 5.0L version of the Fox brake booster. NOTE: The (2.3L) booster on the LEFT can be found in all the non-V8-powered Fox Mustangs, EXCEPT in Fox Mustang convertibles. The boosters in them are like the 5.0L booster on the right. 

1. (Left to right): '67/'68 Mustang MC for power disc brakes. Construction: Cast-iron.
2. Maverick/Comet/Granada/Monarch. Contruction: cast-iron.
3. Pre-'87 Mustang . Construction: Aluminum.
4. '87-'93 Mustang. Construction: Aluminum body, plastic reservoir.

'67/'68 power brake MC mounted to 5.0L booster in a '68 Mustang.

Maverick/Comet/Grananda/Monarch MC on 5.0L booster.

1990 Mustang 5.0L booster/MC mounted next to a JMC hydraulic clutch MC.

1990 Mustang 5.0L booster/MC mounted next to a JMC hydraulic clutch MC.

Pre-'87 Mustang aluminum MC/5.0L booster.

1987-1993 aluminum body/plastic reservoir MC & 5.0L booster.

Notice there is plenty of clearance from tip of MC to back of shock tower.

Basically, the gist of the photos above is to show that you have lots of options in what type of MC you choose to install, even with this 5.0L Fox brake booster being thicker than the 2.3L version, there is still plenty of clearance between the tip of the MC and the back of the shock tower for (most) MCs.

The distance from the firewall to the back of the shocktower, on the '64½-'70 Mustangs, is ~14¼". The overall length of the booster and MC (combined), should be kept at no longer than ~ 14" total to fit within this distance.

Starting with the '94-later Mustangs, the MCs are setup for disc/disc configurations.

Prior to this date, most are for disc/drum setups.

Before '74, most brake systems are setup for drum/drum systems.

Note: These latest update photos were mostly taken in early December '02. The engine compartment no longer looks as it does in these photos, since now it has a fresh coat of semi-flat black paint on it. :-)

Stop safely & stylishly! And happy Mustanging!!