1966 C20 dual-circuit master cylinder

[sodly]

I've read a lot of threads here about upgrading C10s to dual-circuit master cylinders but none about C20s. Do you simply use a 1967-70 C20 master cylinder? Or is there even any difference between a C10 and C20 master cylinder? I'm talking about a stock drum/drum, non-power setup. Thanks!

[f66]

Originally Posted by sodly

I've read a lot of threads here about upgrading C10s to dual-circuit master cylinders but none about C20s. Do you simply use a 1967-70 C20 master cylinder? Or is there even any difference between a C10 and C20 master cylinder? I'm talking about a stock drum/drum, non-power setup. Thanks!

Sodly, use a 67-72 3/4 mc.

[sodly]

Is there any difference between C10 and C20 master cylinders? Or Impalas for that matter?

[jocko]

I'd personally use a 67-70 drum/drum C20 MC, not a 71-72 disk/drum MC.

Post 31 of this thread is the one I had in mind regarding different line routing of C10 vs C20 mcs. NOTE post 31 is relative to a 71, what I still don't know is if the drum/drum mc's of 67-70 used reverse line routing for a C20 like the 71-72 did. That is the real remaining question I believe - once you know that, you'd be good to go to buy a 67-70 C20 MC and install, with or without a distrib block, as long as you hook the front brake curcuit to the proper reservoir and the rear to the proper res, etc. I don't know if Imp mc's are different, but I have seen people use them on C10s at least. I'd personally just by a new 67 C20 mc and run with that approach. And you could always include the distrib block if you want, and not hook it to anything electrically, it just won't server much purpose.

[sodly]

The photo I posted of the low-mile, original 67 C20 in my other thread on the 67-72 side shows (I think) that the plumbing is NOT reversed. When you buy a new master cylinder does it specify which reservoir is which? I would hope so!

[jocko]

I am inclined to believe your assumption is correct (I have the same assumption ) - i.e. that they are not reversed on the drum/drum mc's - but I just don't know for certain. I ran into this issue when I was putting a new MC on a 71, and it was also my first C20... Luckily I discovered this little tidbit before I hooked everything up (because they aren't marked). Need someone on here with an original 67-68 C20 to check which reservoir goes to front and which to back. Hard to tell in pics unless they are close up.

[Captainfab]

With the '67-'70 C10 master cylinders, the front port is for the front brakes. A C20 should have a larger bore but I do not see why the ports would not be the same as a C10 master cylinder.