I mocked up a prototype manual brake system on a 1991 Firebird. This system requires a 2.0” hole to be drilled in the firewall and a 31/64” hole to be drilled in the pedal.
View attachment 128393
The 2.0” hole drilled in the firewall allows the use of the upper two holes that the brake booster bracket utilized and allows a master cylinder to bolt up. This arrangement allows for a 6 to 1 pedal ratio.
View attachment 128401
With a true 6 to 1 pedal ratio and using the upper bolt holes in the firewall, you also get good pushrod alignment with the master cylinder piston. The 31/64” hole, that will be drilled into the brake pedal arm, is good for the ½” stud/pin to be pressed into the pedal with an optimal interference fit with zero stud/pin play. To utilize the ½” stud/pin that is pressed into the brake pedal arm, I made a custom clevis with a ½” hole for the stud/pin. The clevis is machined to use a 5/16” diameter pushrod with fine threads.
Here are the items used for the pushrod assembly.
View attachment 128409
View attachment 128393
The 2.0” hole drilled in the firewall allows the use of the upper two holes that the brake booster bracket utilized and allows a master cylinder to bolt up. This arrangement allows for a 6 to 1 pedal ratio.
View attachment 128401
With a true 6 to 1 pedal ratio and using the upper bolt holes in the firewall, you also get good pushrod alignment with the master cylinder piston. The 31/64” hole, that will be drilled into the brake pedal arm, is good for the ½” stud/pin to be pressed into the pedal with an optimal interference fit with zero stud/pin play. To utilize the ½” stud/pin that is pressed into the brake pedal arm, I made a custom clevis with a ½” hole for the stud/pin. The clevis is machined to use a 5/16” diameter pushrod with fine threads.
Here are the items used for the pushrod assembly.
View attachment 128409