The basis of this 4 wheel disk brake conversion is the adapter brackets manufactured by the Street Rod Manufacturing Company. The rear adapters are designed to bolt to the 8 inch Ford axle housing and the front adapters bolt to the stock Mustang II caliper locations, both using General Motors brake calipers.

A note of warning, which is probably self evident from a project of this nature but can be a second thought, this conversion requires stepping up to 15 inch rims to clear the brake components. 14 inch rims may be acceptable but would require slight trimming on the rear calipers. In testing rims sizes for a spare tire I find that it may be possible to grind away enough of the rear Seville calipers to allow 14 inch rims to fit. But not having pursued this direction I cannot say it would work.

Another opportunity I took advantage of while changing axles and front rotors was to go to a 5 lug 4 1/2 bolt pattern. This change opened up the entire spectrum of aftermarket rims. I have found in the past that the selection of rims for the 4 lug pattern is severely limited with extended order times. My last 4 lug pattern rim purchase for the street took three months for delivery.

The conversion was spread over a period of three years while I was also restifying the rest of the car. As I experienced engineering problems, the project was shelved while I worked on other segments of the car allowing time to do further research and study the problems. I find this slow steady approach to be the best for finding sound solutions which would endure the rigors of safe and hard braking. I believe that with the information presented here the project could be completed in a week of evenings and a full weekend.

Rear Brake Conversion.

I purchased my calipers from a local salvage yard. Although in the long run this was the most expensive approach, it did provide me the emergency brake bracket and lever which do not come with remanufactured calipers. For this reason I still suggest getting the calipers from a salvage yard, and then have them professionally rebuilt with new pistons. If the bores are not properly prepared, then you will have leaks around the pistons which usually results in the contamination of the rear pads. Secondly you will also have fluid leaks around the emergency brake lever shaft.

The Seville emergency brake design matches the Ford cables perfectly. The emergency brake cables are a direct bolt up which was an unexpected surprise, requiring only the lengthening of the emergency brake bracket. I cut the bracket in half and welded in a 1" piece of 1 x 1 inch square tubing with one side cut off (U shaped matching the bracket).

The Mustang II brake cable fits through the emergency brake bracket. I then slipped a stronger return spring over the stock spring and pushed the cable end through the Seville lever. Then take the slack out with the brake lever adjusting nut.

The emergency brake setup when finished

The rear brake hoses were selected based on the need to bolt to the GM Seville calipers to the Ford OEM brake fittings, and minimize the length. The part selected was from the front of a 1979-80 Buick Skyhawk. A bracket needs to be fabricated and welded to the axil housing to provide a rigid platform for the steel brake lines to mate to the caliper hose. The hole in the bracket is not round but conforms to the stepped designed of the flexible hose to allow for tightening.

The brake rotors are from a 1975 - 79 Lincoln Town Car. To fit them onto the axle within the radius of the Seville brake caliper the overall diameter of rotor must be reduce to 11 inches.

The brake pads are from 1980-81 Cadillac Seville, Wagner part number PD7070ARl. They posed a special problem in that the stock pads are too thick in relation to the rotor thickness. The first attempt I made was to use a belt sander in a vice to evenly sand down both pads. The thickness of the pads must be machined down by approximately 3/16 to 1/8 inch on each side. Interference should be evaluated at pad replacement time since rotor turning will change this measurement.

Although this worked I don't recommend it since there is a tendency to rock the pad resulting in a rounded pad face. The following season I found the pads contaminated from a brake fluid leak and need to replace the pads. I found a brake and clutch resurfacing business and had the pads resurfaced with material 3/8 inch thick. This was more costly, but less hassle and even faced pads are assured.

I also used this opportunity to step up to a 5 lug 4 1/2 bolt pattern. This was accomplished by using the Ford Granada 5 lug axles from an 8 inch rear end with a "drop- out" carrier. The axils must be modified as follows to fit the Mustang II axle housing:
* Long axle shortened by 1/8 inch.
* Short axle shortened by 5/16 inch.
* Factory taper at the spline end must be retained to provide proper fit into the carrier.
* The axle bearing flange from the Mustang II axles must be switched over to the Granada axles due to the odd bearing bolt pattern on the Mustang II.
* The axle surface diameter at the point where the bearing is pressed must be machined down in the direction of the face of the flange by 1/8 inch (horizontal to the axle centerline) to allow proper placement of the bearings in the axle housing.

Rear end off the car with rotors fitted
Another shot of the rear end with rotors
Completed rear disk setup on car

As noted previously, the brake rotors are from a 1975 - 79 Lincoln Town Car. These rotors are 5 lug 5 inch bolt pattern. The rotors were taken to the local machine shop and had the 4 1/2 bolt pattern drilled to match the axle bolt pattern.

Front Brake Conversion

The front rotors before the conversion

The front braking was enhanced by using the a Street Rod Manufacturing Company's front adapter brackets. The brackets were designed to accommodate the front disk brake caliper from a 70 series General Motors Camaro with the Ford Granada front brake rotors.

The front brake rotors are 5 lug from a 1976 Granada. These rotors use stock Mustang II wheel bearings and wheel seals, which make for a great swap. These are available new from all parts stores.

After I had acquired the calipers, rebuilt, painted and installed them, I realized that on a lock to lock turn the hose bolt hit the coil spring and limited the turning radius. Research at Summit Racing provided another solution. Wilwood makes an aluminum replacement brake caliper with an alternate hose mounting location which worked; GM II part number 120-0454. The calipers also require special caliper bolts for the Wilwood GM calipers, Wilwood part number 230-0619.

The front brake pads also come from the 1976 Camaro. Like the rear calipers the thickness of the pads must reduced to fit the thickness of the rotors. (See the rear brake conversion brake pad suggestions.

The brake hoses are not stock from the Mustang II, but I did not note the part number in my records. I just asked the part store for brake hoses of sufficient length to fit, with a male end to fit the Mustang II and the banjo end to fit the Camaro caliper.

Completed front disk setup with Wilwood calipers on Granada rotors

Master Cylinder

The master cylinder must provide sufficient volume for 4 calipers instead of the stock two smaller calipers and rear drum sleeves. Through the recommendation of Baer Racing, I used a master cylinder from one of the following: Ford Trunk/Van E250 & E350 1975- 1976, or F250 & F350 1968 - 1976. These master cylinders are a direct bolt-in replacement for the stock Mustang II master cylinder and increase the cylinder volume. New brake lines must be rebent to mate up to the master cylinder.

To get the balance correct between the new front and rear disk brakes I installed a proportioning valve in the rear lines. I used a Wilwood valve part number 260-2220.

One final modification that must be made is the removal of the factory proportioning assembly from the distribution block. This assembly is located under the brass cap with the vent hole, pointing towards the radiator. The spring assembly and seal must be removed to disable the factory proportioning and the vent hold brazed shut.

Epilogue

This conversion is not for the faint hearted. There is a good amount of fabrication required to get the components to work together. The advantage I had was that my Cobra was not my daily driver thus the lengthy down time did not effect my lifestyle other than adding frustration. At the time I started this conversion, there were also no complete kits available, like the SVO kit from Ford Motorsports.

Mark Heschelman also made an interesting comment that I'm giving a lot of thought. He pointed out that if the front spindles are not forged it could be possible that the increased distance from the spindle to the caliper could cause the king pin to fail. I have no answers to this problem. I have been considering a switch to forged dropped spindles and considering this unknown, may speed this change.

After having this conversion in place for one year I find the braking has significantly improved as I had expected. The Seville calipers although plain, function very well in this lighter vehicle and I still have emergency brake! The aluminum Wilwood calipers also tend to flex a lot more than the cast Ford and GM when the brakes are applied, but I have not noticed any problems from this.

1976 MUSTANG II COBRA Special Parts and Assembly Notes

1976 MUSTANG II COBRA 4 - Wheel Disk Brake Conversion

Questions? E-mail Dave Wilson

©1998-2014 The Mustang II Organization, ©1997-2010 D'TechnoArt Designs, & ©1999-2014 Lee Lafountain