The Stovebolt Site Forums The Parking Lot Big Bolts brake/clutch master cylinder question

I hoping that someone here can help to keep me safe. I have a 62 Chevy c-80 that had a leaking master cylinder. I also have a 60 Chevy c-20 that I broke one of the rear trailing arms on. I have since swapped the master cylinders, but haven't attempted to drive the big truck yet. Will the smaller bore sizes from the c-20 have a negative effect on the braking (and clutch) performance of this truck?

Thanks,
Kael

How much smaller is the C-20 master? If there is a big difference, you are better off getting a new master or rebuilding the one you have. If it is a small difference you should be able to drive it. When the truck has a load on it is when you will have problems.

Personally,I wouldn't take the chance.There is a big difference in curb weight between the 3/4 ton C-20 and the C-80.Maybe you can get away with it in Wisconsin,but I am in New York where most folks drive funny.

If master is too small, you won't be able to get solid pedal or none, even tho all is bled good. Even smaller amounts like 1/8" make a big diff. I didn't believe it, and tried it, never did have good brakes, till I got correct size Master. 80 series is a Big rig, close to 1-1/2" bore I bet, and 20 series only has about 1". Am I correct? The clutch sides are usually 15/16", and may stay the same on those.
It's about "Volume" needed to run all the brakes, not just Pressure.

Thanks,
That is what I expected to hear. I don't remember the bore sizes right now although there is a difference of about 1/8". The biggest reason that I swapped it out originally is that I was quoted a price between $425 & $780 for a new replacement of the one that was on my truck when I got it. I later found out that the one on it was not the original one anyway. I am still looking at finding a reasonably priced replacement. Until then, the truck stays parked.

Kael

Maybe you can find a company that can rebuild the master for you. Might be cheaper than buying new

Put kits in it. It,s easy to do. Get a brake cyl. hone. If it has pits that wont come out you can get them sleeved.

Where can you get the proper rebuild kits for the 61 11/2 ton clutch/brake master cylinder? I got one from O'Relliey and it's the wrong one listed in there book.Both units bleed off.