Problem with my power brakes

[67F10YR]

I just put power brakes in my '67 F-100. The donor truck was a '72. Everything went together like they were supposed to, but when I tried them out I found they were stuck on slightly, so I was dragging the brakes a little. I used my stock master cylinder from the '67 and bolted it right onto the '72 booster but I used a brake pedal bracket from a '69 because it had the 5" distance that was needed and it also had the same neck as my '67 so it fit nicely at the dash cutout. That should be alright, shouldn't it? I have the shaft tightened as far in as it will go but it's just not quite enough. What can I do? Are there shorter shafts for that booster? It only needs to be maybe 1/4" or so. Any ideas?

[fordman]

most boosters have two adjustments to them. one is to the brake pedal. not all boosters have that. the other is between the booster and the master cylinder. that is probably where the problem is if the brakes arent retuning all the way. just a little adjustment will let the master close all the way to return the fluid and let the brake not drag.

[67F10YR]

I have the shaft to the master cylinder screwed all the way in now. Before I left work yesterday, I pulled the master cylinder off and found that I still had a half turn left, so I screwed it in tight. The brakes worked perfectly then....for about 15 miles when I parked it for a few minutes. When I started it again the brakes were locked up tight. I called for a tow truck, but while I was waiting I called a friend that lived near by. He came down and looked things over and reasoned that if we couldn't shorten up the shaft anymore, then we might try moving the master cylinder out away from the booster a little. So we found a few washers and put two on each side, moving the master cylinder out about 3/16", and tightened it down. It was perfect..... again. But I wondered if they would do the same thing and lock up after a short while, but no......they seem to be fine now. Another friend of a mine, a mechanic, told me that was an ok temporary fix, but something else should be done as a permanent fix. He didn't like the gap between the booster and master cylinder. Any thoughts about this?

[fordman]

here is a guess. the 67 master has a different storke than the 68-72 master. maybe you need a different master.

[Hemmi06]

Just one thing to consider: Air in the lines/MC? I had this issue and caused the same thing you are describing. I bled the lines and everything worked great for a while then it happened again. Air was getting into the MC. I ended up replacing the MC and rear wheel cylinders. Might want to check the air possibility. Just my

[fordman]

it could be air also. something is making the fluid not return to the master once the pedal is let off.

[fmartin_gila1]

I have had to resort to making a spacer in the past in order to get freeplay, sounds like you are on the right track with the components you are working with. Once you get it spaced out, you will probably have to lengthen the pushrod in order to get proper freeplay.

Fred