Dual chamber master cylinder for drum brakes

[V8 Bob]

Originally Posted by KULTULZ

Just a warning, beware of these so-called disc brake changeover vendors. Few seem to have full comprehension and now are supplying off-shore parts.

Case in point, this individual went to an EvilBay vendor with a four wheel manual drum pickup and talked to the guy. Said he wanted power dual reservoir drum for now but would like to add front disc later.

Below are photos of what he was sold and installed-

Now he has to can it and start over.

All he has to do is switch the lines going into the combo valve, so the secondary (smaller) rear brake M/C chamber goes between the prop valve adjuster and pressure switch, and the larger front M/C chamber goes to the front of the pressure switch with the two output ports. When front discs are installed, removal of the red 10 lb residual is all that's needed.

[KULTULZ]

Originally Posted by V8 Bob

All he has to do is switch the lines going into the combo valve, so the secondary (smaller) rear brake M/C chamber goes between the prop valve adjuster and pressure switch, and the larger front M/C chamber goes to the front of the pressure switch with the two output ports. When front discs are installed, removal of the red 10 lb residual is all that's needed.

Why would one install an ADJUSTABLE BRAKING BIAS VALVE on a four wheel drum application? All he wanted was a split reservoir w/ booster. Did the vendor a$$-u-me the secondary circuit has an internal RPV? What about MC bore size?

All replacement MC's for that period do not include RPV(s) as later applications (1974- ) did not use an RPV and the deletion reduces inventory.

You see value in what he was sold? You would modify yours or a customers car in such a manner?

[V8 Bob]

KULTULZ,
You're right. I somehow confused this thread with one where front discs were going to sometime replace the drums. My bad!

[KULTULZ]

You're OK ...

The buyer stated to the vendor that he was considering a disc upgrade in the future ($$$) and for now only wanted a boosted split system and instead of the vendor supplying only the correct drum system upgrade sold him a system which is totally unsafe.

HEY! Anytime you see or feel I have posted something incorrect, feel free to correct. I am not proud and learn something new everyday even on older vehicles.

I was starting to have self-doubt there.

[V8 Bob]

Originally Posted by KULTULZ

You're OK ...

The buyer stated to the vendor that he was considering a disc upgrade in the future ($$$) and for now only wanted a boosted split system and instead of the vendor supplying only the correct drum system upgrade sold him a system which is totally unsafe.

HEY! Anytime you see or feel I have posted something incorrect, feel free to correct. I am not proud and learn something new everyday even on older vehicles.

I was starting to have self-doubt there.

I have to disagree with you on the system being totally unsafe. The only thing unsafe was the incorrect M/C plumbing, as I pointed out earlier. I would have also included an adjustable proportioning valve with the intent to upgrade the front drums to discs, minimizing additional plumbing changes and costs later on.

As far as the proportioning valve, turning the knob CW to fully open the valve raises the split point about 1000-1200 psi, well above the normal drum brake operating pressures-in effect bypassing any proportioning to the rear drums.

[KULTULZ]

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We will have to agree to disagree.

No foul, no harm.

[paul2748]

If you want the skinny on what master to use, go to the experts make and sell conversion parts. Try Engineered Components Inc (ECI) in Conn. for advice. They make all kinds of kits for brake conversions.

[KULTULZ]

Originally Posted by paul2748

If you want the skinny on what master to use, go to the experts make and sell conversion parts. Try Engineered Components Inc (ECI) in Conn. for advice. They make all kinds of kits for brake conversions.

Just what is needed, another kit assembler offering GM components for a FORD. Wonder how much of it is off-shore?

That CORVETTE MC goes well with the INTERSTATE BATTERY and STANT radiator cap.