Technical 60 Chevy truck brake/clutch mc as 2 pot brake mc?

So I found a thread on here about running the 60's Chevy truck brake/clutch mc as strictly a brake mc.

The only opinion on it was "you can't do that"

If this is true, can somebody explain why?

I know the brake side has a 1" bore and the clutch has 1.125" bore, but it could be sleeved down to a 1".

Why wouldn't this work?

 

Why make it complicated? just use the original m/c

 

I don't want it under the floor and I am scared to run a single...

 

dang kids these days.... some of us have been driving around with single master cylinders for decades.

 

If your running discs on the front the 1.125 bore should be ok. Nothing like a double post to keep us running around in circles.

 

You could use the exercise. I'm just here to help.

 

Do you know if the truck mc is a true dual reservoir?

 

If I recall correctly they are separate and it has a boss in the middle for the cap bolt to thread into. I think you have a good idea and if you incorporate a balance bar you can proportion the brakes front to rear, no need to sleeve it. Check out the dual brake masters and clutch master we did on the modified.
http://www.jalopyjournal.com/forum/threads/26-7-t-modified-build-all-ford-by-ford.534292/

 

You seem to be wanting the safety benefit from a dual circuit mastercylinder system, but I don't think what you are proposing will accomplish that. The reason being, if one of the twin cylinders fails, the balance bar will have no resistance at all on the failed side and will not transfer all the pedal motion to the remaining good cylinder. The geometry will change unfavorably. With a true dual circuit M/C the pistons are, as you know, in tandem, and the failure of one does not change the geometry of the pedal mechanism, though it might affect travel a small amount.

The 'balance bar' system was not commonly employed to offer dual brake system safety, but as a means of easily adjusting brake bias, front to rear, or perhaps, even side to side (roundly round), on racing car appications.

Ray

 

Gotcha. That makes sense. I could devise a design that doesn't "balance" but achieves the desired result.

 

I looked at running the Wildwood triple under dash set up... If my idea won't work then I guess that's my next option.

 

...or just use a single brake M/C, like everyone did in 1964.

 

Deto,

I have seen it done but only on brake systems that were not properly balanced as in the front and the rear needs different bore masters to work properly not balanced.

If you want to do something totally trad and different from the more modern solution get yourself two jelly jar master cylinders. They are the most common single master made, readily available at any auto parts counter ( think '65 Chevy truck here or '65 galaxie) and cheap. Now mount them side by side on the firewall and use a balance bar between the operated by your brake peddle.

Simple and different than what you commonly see.

 

I thought about running that set up. Hopefully it will fit on the firewall access panel on 49-54 Chevy sedans

 

Deto, I just tried this a few months ago and here is the real problem. If you intend to transplant a hang pedal assembly anything similar to the geometry of the one the BMC/CMC work in you more than double the pedal pressure required to generate the previous pressure needed to stop the car at the wheel cylinder. By splitting the MC you go from 0.785" squared piston area to 1.78" squared piston area at the MC. With similar pedal geometry your pedal pressure increases by 2.26X

 

You just have to grab the emergency brake and pull it.

 

If you read Cody Walls thread on his (amazing) '59 Chevy wagon real close you find a mention that he sleeved his "Dual Master Cylinder" down to something under 3/4" I think. You can do the math by calculating the present master cylinder piston area, the total wheel cylinder area it applies pressure to, and the mechanical advantage the pedal geometry applies. If you can match all those with a dual master, or add power assist, you might end up with something that works. Or do as Jim suggests and stick with what GM designed that has worked for decades.

 

What's wrong with running it under the floor? Sure it's not quite as convenient but set up correctly you shouldn't have to mess with it much at all. They make slick dual floor units.

 

Didn't even think of that. Good call.

 

For what it is worth....
Classic parts of America makes a bracket that will allow you to use a 67 or 68 chevy dual pot M/C. They also sell the M/C if you want to get it from them.

I know it doesn't answer the question but you do get a dual pot M/C; though it is under floor. If you suck at metal fab as much as I do you can do a bolt in.

I have pondered a dual master in my truck since city driving involves a lot of morons that tailgate and panic stop.

 

adding a dual M/C will not make the brakes work better, it will only help prevent a catastrophe due to parts failure, such as a leak in the system. But only if you install the dual M/C properly...you need to check that it's working right, by opening a bleeder and see if you still have pedal. Repeat with a bleeder at the other end of the vehicle..

 

Not sure if this is gonna help, but here's what I built for my AD truck.



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