Disc drum master cylinder conversion issues

[KMAT]

I'm having trouble finding the correct master cylinder for my 70 C10 pickup disc front drum back the rod goes into the back of master cylinder is too long for the master cylinders that I've been giving any information will be greatly appreciated

[rpmerf]

What master cylinder and booster are you using / have tried?

[KMAT]

Ive left old booster on and had parts store order me a M.C. for disc drum from 1974-86 truck.and it used a short rod,and mine is adjustable long rod.
They ordered one for a early to mid chevy car,and it also used a short rod.
I am on a tight budget,like most, and cant afford a master/booster combo.

[70STOVEBOLT]

Try one for 71-72 truck, unless the booster is not original.

[tx71smallblock]

a 71-72 should be a direct replacement, just make sure if you have power or manual you have to get the same in replacement.

[KMAT]

I believe this to be the original booster. Although when i baught the truck it had front suspension disc set up on already, previous owner could not remember what it came off.Also the back drums lines were cut and crimped.I am trying to get brakes to work properly. Complete rear drum rebuild, replaced bad lines front and back,new calipers,pads and installing proportioning valve inplace of indicator block switch. I will try post pictures of what i have.
THANK YOU!!!!!. For feed back and help.So much help ive received here.

[70STOVEBOLT]

That looks to be a 3/4 or 1-ton style booster

[KMAT]

Oh okay well that's the one that came with the truck when I bought it a friend of mine did drop one off the other day wasn't sure what came off of wasn't sure if it's good or not it has a short shaft and a very heavy Rod that goes to the pedal. I'm not sure if it's good the only way to test today filming is to put it on and try it if I get the right master cylinder

[70STOVEBOLT]

That one does not look right either. Should look like one of these in the pics. The one on the left is a Delco Moraine type and the one on the right is a Bendix type. Either of these will work with a 71-72 C10 master cylinder.

[demian5]

You have the wrong booster on the truck and as a spare. I originally have a power brake drum 1970. I converted to disc. I also had to replace the booster as it was bad. I purchased on for a 1970 half ton truck and it was exactly the same as the one I pulled off. No issues at all and the disc/drum master worked fine when I converted to discs.

Order one for a 1970 1/2 ton truck and you will be fine. Centric makes one - 160.80031

[70STOVEBOLT]

Originally Posted by demian5

You have the wrong booster on the truck and as a spare. I originally have a power brake drum 1970. I converted to disc. I also had to replace the booster as it was bad. I purchased on for a 1970 half ton truck and it was exactly the same as the one I pulled off. No issues at all and the disc/drum master worked fine when I converted to discs.

Order one for a 1970 1/2 ton truck and you will be fine. Centric makes one - 160.80031

Did you use a 71-72 master cylinder?

[demian5]

Yes

[KMAT]

I really appreciate all of the input that I've gotten regarding this issue I really do.
Someone once said there is no stupid question, so here's a stupid question, what would happen if I used one of these two brake boosters if they were good, a brake booster is a brake booster they all do the same thing correct? I'm just asking. From what I understand brake boosters do I would not think that it would matter which are used but I'm not sure that's why I'm asking.
Once again all the answers and help that I've gotten on this site have been so helpful.

[franken]

Define these. You've introduced an unintroduced pronoun, which by definition is meaningless.

[KMAT]

Fine be that way what would happen if I used one or the other of the brake boosters is that better

[70STOVEBOLT]

Originally Posted by franken

Define these. You've introduced an unintroduced pronoun, which by definition is meaningless.

He means the ones he showed pics of earlier in the thread.

Yes you could use either one if they are good, provided you use the correct master cylinder, and you make sure the pedal linkage rod is the correct length.

[KMAT]

Thanks 70STOVEBOLT,
I was kind of afraid you might say something like that which brings another challenge I think I do have the right master cylinder now and the rod coming out of this brake booster to the pedal is the one that came with the truck when I bought it. And yes it may be wrong but that's why we have this kind of a Chevy truck. Com site so I can ask questions and get good answers because there is not a whole lot of information that I've been able to find on the internet or YouTube unless I'm not looking at the right websites. I guess next comes Plumbing everything and mounting proportioning valve someplace thanks for your help 70STOVEBOLT.

Really appreciate it the input

[70STOVEBOLT]

Sounds like you got it figured out. Let us know how it works out.

[KMAT]

Will you know a person should do a little bit more research vehicle to make sure they know what they have and since I've been having this brake booster master cylinder issue did some checking on the VIN numbers and my cab did come off a a 3/4 ton pick up which is why the booster looks like one off of 3/4 ton therefore I appreciate all of the information that everybody is giving me now fourth trip back to the part store for a 3/4 ton master cylinder and if I read earlier on a post or a thread I'm 3/4 tons I have to switch the lines going to the proportioning valve back Reservoir front portion valve front master cylinder line the back portion valve please correct me if I'm wrong thanks every everybody for all the great replies that's why I joined this site

[michael bustamante]

see I didn't know the 3/4 ton had a different master cylinder either. booster yes. I have a 71-72 prop valve assy for sale if you end up needing that also. itll have the two lines going to the master cylinder.
watching this thread....
what did you find out about the pushrod to the master cyl?

[KMAT]

Thanks Michael I'll let you know about the proportioning valve, and yes the master cylinder is way bigger and heavier for 3/4 ton and 1/2 ton I'm hoping that my brakes work okay being the truck 1/2 ton in the booster and master cylinder is a 3/4 ton. They still have some more research to do regarding the brake lines from the master cylinder to the proportioning valve. I recall a post somewhere that said I need to switch the lines going down to the proportioning valve I need to find where that thread was to verify

[KMAT]

Yeah 70 stovebolt I still have the wrong master cylinder on that booster after checking the VIN number on the cab came off a 3/4 ton truck so I had to get a another master cylinder for that booster

[70STOVEBOLT]

I do not know much about the 3/4 ton master/booster setups, but check the thread below and I think it will answer your question.

http://67-72chevytrucks.com/vboard/s...d.php?t=478154