brake booster question

[krazy_texan]

ok i could not find a definate answer on this using search. Watch now that i said that someone is going to pop up with a link in like 2 seconds to a search that has exactly what i am looking for lol.

Ok so i am wondering if there is a difference in brake boosters for disk brake trucks and drum brake trucks. i just got a smoking deal on a rebuilt master cylinder for a 68 master cylinder off of rock auto for $6 but now need a booster would a 71 and later booster work with a 68 master cylinder running a drum drum setup. I plan on putting this on my 65.

[sanford66]

The boosters should be the same from disk to drum trucks. The differance would be the proportioning valve. The valve would be different between a disc/drum truck and a drum/drum brake truck. I'm sure others will chime in with the specifics though. Joseph

[jocko]

Is your 68 master cyl for manual or power brakes?

Note that the piston is different in a power brake master cylinder and a manual brake cylinder. Power brake mc will have a shallow indent in the back of the piston where the booster's pushrod inserts. The manual mc has a much deeper indent in the back of the piston for the brake pedal pushrod to insert. If you mix/match, no workie so good unless you somehow extend the booster's pushrod to mimic a manual brake pushrod setup.

edit - also note, if you are 4 wheel drums, a prop valve is not required. The master cylinder itself is designed to feed front brakes slightly before the rears. Also note when hooking up lines - the forward connection on the master (closest to the grille) is for the rear brakes and the aft (closest to the firewall) is for the front brakes. If you reverse these on a drum/drum setup, mc's internal proportioning won't work right.

You CAN use a prop valve if you want to fine tune, but it's somewhat redundant and not required on a 4 wheel drum setup.

[jocko]

here's a diagram of the drum/drum mc (courtesy of chief rocka):

[krazy_texan]

I have gone through most of these issues but after driving the truck tonight i just really want to upgrade to power brakes i have alreaday split my brakelines but because of the incompetance of said auto parts store employees i just teed it off under the hood and went back to a stock single master cylinder temporarily because they gave me 3 wrong master cylinders before that. they kept giving me ones for power brake trucks and i could not get my brakes to bleed cause i dont currently have a booster on the truck. i plan on keeping the drums for now i just wanted to make sure that there was no difference in the boosters so i could probably broaden my search for a good used one.