Converting from single circuit to dual circuit brakes... because we like our windshield WITHOUT our faces thrown through it!
(article by Jim Gauldin)
I know the purists will cringe when I say this, but single circuit brakes are no more than an accident waiting to happen. This very car was wrecked once because the single circuit master cylinder went Tango Uniform at a very inopportune time, and it almost happened a second time while Amelia's mom was driving the car with Amelia in the passenger seat; Amelia's mom was pumping the brake pedal like an organist on crack while Amelia reached across her lap and yanked the hand brake. Hey, those tiny drum brakes give me the heebie-jeebies WITHOUT the thought of losing everything when one wheel cylinder goes south. It makes me cringe at car shows when I see nice cars, driven from many miles away, still sporting the mason jar death trap on the firewall. Those people must be living right. The Feds mandated dual circuit brakes beginning with the 1967 model year for good reason!
Out with the old and in with the not-quite-so-old, as we transplant a 1972 Maverick master cylinder into the Bird!
When we converted our '63 Falcon from single circuit to dual circuit brakes, we faced the dilemma of how to integrate the hydraulic brake light switch to the new, dual circuit hydraulics. Unlike the original '63 master cylinder, our later model Maverick master cylinder had no provisions for the switch. Many people who have done this swap use a tee and keep the original hydraulic switch. I decided to change to something more like you'd find on a later model car - an under dash mechanical switch attached to the brake pedal.
First, I removed the brake pedal and the brake pedal support structure. It's really easy. Remove the bolt that holds the master cylinder pushrod to the pedal mechanism. There are 4 bolts under the hood that attach though the firewall. 2 of these 4 bolts also hold the master cylinder to the firewall. Under the dash, there is a single sheet metal screw that holds the pedal support to the firewall. Also, there are the 2 bolts that hold the steering column to the dash (under the speedometer). Remove these 6 bolts and 1 screw and the pedal and the pedal support structure will drop right out. I removed the pedal and the structure separately, but it should come out in one piece.
I purchased a Micro Switch at the local electronics supply house. You may find the Micro Switch brand, and you may find a generic replacement - either will work just fine. This is a very common switch that is used in a variety of industrial applications. Just show the counter jockey one of these pictures and he'll know exactly what you want.
After the support structure is back in the car, locate the wiring bulkhead where wires go from the passenger compartment to the under hood area. Find 2 green wires located side-by-side in the top plug, bottom row, right (passenger) side. Cut these wires and attach them to the new wires on your Micro Switch.
Adjust the Micro Switch so the brake lights turn on when the pedal is pressed slightly, but be sure they always turn off when the pedal is released.
Our dual circuit '70 Maverick master cylinder looks like it was born there! We had to do a small amount of plumbing to accomodate the Maverick's driver-side hydraulic fittings.