icanfixall
Official GMM hand model
As some of you know there has been plenty of discussions about changing out the vacuum to hydroboost and the master cylinders. Here is what I have found. Most feel the pressure you need to make a 1 5/16 inch master cylinder work will be felt. Well thats not true. I looked at an F450 system. It has the ten lug wheels along with the 1 5/16 inch master cylinder and here is the kicker. The brake peddle pin that the hydroboost attaches to is 3/4 of an inch higher up on the peddle arm. So that alone gives you much more leverage but at a cost of less travel. But remember the larger master cylinder..... So what I did was changed out the 350 brake peddle for the 450 barke peddle. I will be using the smaller 1 1/4 inch master cylinder so the peddle effort will be no differance. I may use the 1 5/16 master cylinder too. It just depends on how lucky I feel. Both peddles are the same length overall but I did find an early dually 6.9 (less motor) that had a larger peddle main shaft size so don't go trying to make one of those fit your 89 or 90 truck.
