Correct Master Cylinder

[DaHos]

Has anyone since found a source for the correct master?

[70STOVEBOLT]

I'm no expert, but since the OP has the Delco-Moraine style booster, he may need the appropriate master cylinder to match it. My truck has a Bendix booster, and I am using the master cylinder pictured in post #8 on top of the ACDelco box. I added disc brakes to my '70 using 1971 model year info to get parts. I am using the stock cast iron combo valve. The booster was a used part I bought off the parts board many years ago when I still had the drum brakes all around. It worked fine with the stock drum brake master cylinder. Hope this info helps, rather than adding confusion.

[samkost]

Originally Posted by DaHos

Has anyone since found a source for the correct master?

I have not been able to locate an original style Master Cylinder replacement from many inquiries and vendor avenues.
Why AC Delco and the Chinese don’t offer an OE style double bail master is unexplainable.
I thought it would be an easy fix to replace but we all know the extra dollars we are forced spend restoring our trucks!
Still looking, not holding my breath and will probably rebuild my current brake components.
Thanks for the replies.

[cericd]

A few years ago I was swapping my 1970 2wd C/10 from manual 4 wheel drums to a factory style 1971 front disc rear drum, 5 lug, power brake setup. I did some research on the forum and eventually purchased a restored Delco/Moraine booster and a rebuilt master cylinder (for a 1971 2wd C/10) from Autozone part number M1494 that looks like the Delco unit posted earlier by 1970cstblazer. The one I got from Autozone is no longer listed on their site. Your thread has got me thinking about my setup and I was looking around the forum and ran across someone saying that GM used two different suppliers for these trucks, either Delco or Bendix. They said if you had a Delco booster you would have a single side flip up bail master cylinder and if you had a Bendix booster you would have a double end-to-end flip up master cylinder. I don't know if that's correct since my truck didn't originally have either. However, NAPA lists a master cylinder that looks like my double bail unit here. Dorman also offers one that looks correct here but we know pictures can be outdated. I don't know if either of these are what you're looking for but it gives you a couple things to look at, if you haven't already. I also want to use an original/correct cast iron prop valve and have bought a couple different units. Once I figure out which one is correct I plan to have it rebuilt.

[HO455]

Originally Posted by samkost

Just trying to replace my current 50 year+ set up which worked flawlessly before the restoration shop mishaps.
I also want to maintain the current original cast iron proportioning valve.
Having several forum members here post responses to my questions,
I have been told that this AC Delco/GM part # 18M1036 master cylinder is the correct replacement for my 72’ C10 with SPID code J70 Hydro Brake Booster, with original front disc/rear drum.
Unfortunately the O.E. replacement parts are not readily available anymore and AC Delco has replaced the older 2 bail design with the single style bail.
I may go with a Corvette or Camaro style master (deep bore) brake cylinder.
My booster came from P.O.L. I will try them for a compatible master cylinder.

Still waiting for the local GM dealership to locate an older master replacement.

If the master cylinder worked before I would disassemble it and inspect the bore. If it isn't pitted or scored then get a rebuild kit and install it. There are numerous videos on how to do rebuild a master cylinder. It's a pretty easy job.

[samkost]

Once again,
All vendors web stores show a photo of the Master that I have been trying to locate.
NAPA for example shows on their web site and in store computer the OE photo but in the box is a single bale (new) design not the original double bale.
I’ve been unsuccessful in locating an older OE style stashed anway anywhere.
Auto box stores, the same results.
Old depiction photo but new design in the box.
Frustrating.
Yes, a rebuild of my current Master is the next step.

[weq92f]

.

I recently replaced my MC and learned a few things in the process. What I didn't really understand until now is the picture not matching what's in the box is common. I ordered 1972 C10 MC. The picture on their parts house screen showed different sized reservoirs and a cast MC. What came in the box was an aluminum double same size bowl with two hold down loops. What I cared about was the 1 1/8 inch bore and dimensions being very close to the outgoing MC.

According to CPP, the deep vs. shallow MC piston hole works out simply to power vs. manual brakes. Otherwise the MC is the same. CPP offers a little puck to place in the MC deep piston hole to make it a shallow hole (it is proprietary to their MCs). Boosters are often delivered with both a long and short plunger rod going toward MC for the purpose of accommodating either type MC. As I understand things, these deep/shallow piston and long/short pushrod from booster are standard lengths all to accommodate either type.

-Kevin