I am having trouble understanding how to keep the brake from hitting the engine side of the firewall through adjusting the Toe Board Clearance. With the spring pulling back it is not clear to me that there is any adjust that is going to stop the brake pedal from hitting the fresh paint of the firewall. I know there are bumpers available, but I have not seen them pictured in any of my publications. I have added a dual diaphragm master cylinder in place of the original but I do not believe that matters.
Last edited by ChevyDarren; 05/27/20221:58 PM.
Darren Current Project - 1950 3100 5 Window with a rebuilt 216 and 3 speed trans
No bumper on the brake. Only the clutch has a bumper. In most designs, the master cylinder internally limits the pushrod from being pulled out completely. I would check this on your master cylinder. Maybe it's different. The master cylinder is not strong enough to push the brake arm and pedal back to a normal position so the assistance of a return spring is needed.
Last edited by buoymaker; 05/27/20222:16 AM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
Harold go back and read the poster's question again. He knows he can add a bumper on the brake arm but he wants to know why should he need to when the truck came from the factory without one. He knows there is a problem. Got any ideas?
Last edited by buoymaker; 05/27/20223:55 AM.
"Adding CFM to a truck will only help at engine speeds you don't want to use." "I found there was nothing to gain beyond 400 CFM."
I still can’t understand how adjusting the push rod would limit the clearance if the spring is pulling the brake forward. I can understand that the 13/16 clearance you are looking for is the distance between the toe board and before the master cylinder is engaged. But without a bumper I don’t see how you prevent the brake pedal from contacting the firewall/toe board.
Last edited by ChevyDarren; 05/27/20223:29 PM.
Darren Current Project - 1950 3100 5 Window with a rebuilt 216 and 3 speed trans
The master cylinder has a stop (C clip) that prevents the piston from coming out. The factory setup had a rod that is attached to the piston. This push/pull rod is attached to the brake pedal. Adjusting the length of this rod gives you the clearance that is specified.
If you change the master cylinder to a more modern one where the rod is not attached to the piston so it's simply a push only rod, then the pedal can be pulled back by the external spring and it can contact the cab. (or stopped by the brake light switch)
OK, that that clears things up. If you have replaced or upgraded the master cylinder you will need to use a bumper to stop the travel of the brake pedal. I did not realize this because I replaced the master cylinder after the cab was removed from the frame. Once the cab was back on the frame, it was clear I had a problem that needed resolved.
Last edited by ChevyDarren; 05/27/20229:31 PM.
Darren Current Project - 1950 3100 5 Window with a rebuilt 216 and 3 speed trans
