I pulled (well, the yard pulled) the brake pedal assembly off a 1992 F-450 with a 7.3 diesel and manual trans. The pedal bushing housing diameter was significantly larger than my Bronco pedal. It wasn’t going to be a straightforward swap.

I chose to remove the pin and will relocate it for my hydroboost conversion. I have access to good welding friends that can make it look like the original hole was never there. Same friends will backweld it after the pin is relocated.

 

All the conversions I’ve read say to raise the pin about 3/4” if using a ‘90s hydroboost. Otherwise the rod will be at a funky angle. I’m actually using a hydroboost from a 6.0 diesel but using the mounting bracket from the ‘92 hydroboost. The stock Bronco M/C bolt pattern fits without modifications although it’s looking like I’ll need a 0.060” shim to prevent the M/C from preloading the hydroboost.

Raising the pin will reduce the axial displacement of the MC pushrod relative to the brake pedal. My guess is that will mimic the usual brake pedal displacement drivers’ are used to for the same braking force using a vacuum booster.

 

That is right, at extreme angles of the rod it will make the problem worse than putting the rod at a shallower angle that doesnt side load/bind. That is one thing you have to do with conversions when you are cobbling together parts on something they were never designed for, you have to find a happy middle ground and make scrafices.

Just about all hydroboost you source will be a '90s hydroboost. Ford used hydroboost on their F-super duty series for just a few years at the tail end of the 1980s and they arent exactly that easy to find compared to the 1990 and newer units. If you buy an aftermarket unit such as from hydratech they are post 1990 GM units that is mounted on their custom mounting plate. hydratech how ever tells you to use the stock Power Brake pin location unless the instructions specify you to relocate the pin, every one Ive seen had the pin when it was recommended to be relocated was to relocate it down not up.

Raising the pin allows more force to be put upon the booster for a given pressure applied to the pedal. Its simple mechanical advantage, longer a rod is the more leverage you have. Raising the hydraboost rod higher up on the brake pedal makes the brake pedal longer and giving you more leverage and this is what cause touchy brakes. Every hydraboost Ive installed as a conversion without relocating the pin lower has resulted in the customers hating the hydraboost due to how touchy the brakes are. You cant even rest your foot on them without it feeling like you are mashing on the brakes trying to lock the wheels up.

Just remember you are better off keeping your hydraboost on the stock power brake pin over moving it up. moving it up will make the pedal touchy and there is no shimming to stopping this as the pushrod on the hydraboost is made into the assembly. As far as the master cylinder goes, you want a decent air gap between the booster pushrod and your master cylinder, if you have it touching it can actually have the hydraboost apply itself full brake pedal to the floor upon start up. Ive seen it happen before.

 

FWIW, here's the "How To"

https://www.ford-trucks.com/forums/1...-write-up.html