Rayfry

Can anyone out there tell me which master cylinder to use? I am converting my 63 Vette from drum brakes to disc. Do I also need a proportioning valve?

MikeM

If you're swapping in '65/later Corvette disc brakes, just use the '65/'66 master cylinder. No need for a proportioning valve. That's taken care of by the piston size in the calipers.

Powershift

I would either buy a complete conversion kit from one of the major suppliers(which should include the MC) or use the MC and lines from a 1967. The 1967 MC is not as expensive as the others, is a dual MC, and the associated lines can be run without lifting the body.

As Mike stated, no proportioning valve is needed, although the 1967 system did use a "differential pressure alarm" block.

Larry

Rayfry

I have a Wilwood kit on the front but using 65 vette parts on rear brakes. Will the 65/66 master cylinder still work?

Frankie the Fink

I have a non-power all drum brake '63 - I'll be following the answers

Frankie the Fink

Maybe that explains why my '61 front conversion from '73 Camaro parts works so well without the proportioning valve - never heard that explanation before

Powershift

The correct disc brake 1965 MC or a 1966 MC should work for your conversion. They are single reservoir MC units.

Larry

Powershift

In general, drum-drum or disk-disk brake systems do not need a proportioning valve. The size of the OEM wheel cylinders or caliper pistons are sized to allow this. For special racing applications, this does not always apply, and a proportioning valve may be used/installed. The Corvette J56 brake option was like this.

For cars with disk-drum systems, a proportioning valve is generally needed to get the best braking and to keep the rear drum from locking. I believe that the corresponding MC also has a reisdual/check valve in the drum circuit to keep some residual pressure on the brake shoes.

The best bet is generally to buy a "matched system" from one of the bigger suppliers, or use a complete system from a donor car.

Larry

Rayfry

The 67 master cylinder has a dual reservoir which would make a safer braking system. Am i correct on that point?

Powershift

Yes……...

Larry


EDIT: My comments are based on 1965-66 manual brake system, which used a single reservoir. The 1965-66 POWER BRAKE systems used a special dual reservoir MC. These MC are hard to get and very costly if you have to buy one. They have recently been reproduced, but the cost is still $$$$$. CSSB, Inc. website has pics of these MC, including prices. They are the company that is reproducing these MC for the hobby.

MikeM

They are safer as long as the front/rear seals are still holding inside the cylinder.

Rayfry

OK thanks for all the help. Now back out to the garage. I'll let you know how this conversion turns out.

rtruman

I ordered the kit for my 63 had the duel master and moved the front line up to attach to the dual master with proportioning valve .No cutting ;lines bolt on kit worked great, around 900.00

Powershift

Was is a "proportioning valve" or the "brake differential pressure" valve?

PV not needed for most disc-disc systems, only disc-drum systems.

Larry

rtruman

I had disk on front and left the back drum

Fimpala1968

My car is 64 power brake and single master cylinder and I want to change to dual master cylinder. Which is better bore size, 1" or 1 1/8", if I am driving drum/drum do I have to use the proportioning valve or metering valve, thanks ?

rtruman

The kit I used on my first 63 had disk on front, drum on back and came with dual master with proportioning valve . It worked fine
I was going to do this 63 when I got it ,this one had power brake unit
and I swear its as good or better than the kit. I left it stock with both drums works fine .

TCracingCA

A lot of different directions to go with.

All depends on what brakes you plan on getting.

If you go with one of the kits with front discs and their master cylinder and if they sell you a proportioning valve, then I would say it is not sized perfectly whether that be at the line diameters, or the piston diameters, the MC size, etc. then the proportioning valve would be an essential (and one that is adjustable, and we are not talking about the brake bias switch that is by uneducated sometimes called a Proportioning valve.

If you go with a specific year and swap all four corners, then depending on what year a proportioning valve would not be needed to hang stock calipers and the matching year MC, if the line to the rear is the same diameter. Which would be the normal recommendation!

If you move up to the 1967 and I think mid 66 and up, then I believe that you had better run a proportioning valve if you don't plan to run a new diameter line to the back.

The MC piston diameter will effect the pedal pressures (more or less leverage essentially) and if assembling it yourself with different year components, then you want to check your engineering and make sure you have a realistic pedal pressure, pedal travel, pad engagement etc... etc..

If you go with the Wilwoods or Brembos or whatever and such, then I don't suggest mixing there stuff with other stuff, unless they are indicating that it is compatible and even then I would only do their entire 4 corner set ups! Would be my recommendation. This reasoning would evolve into an entire engineering discussion that would cause the Vendor to have the thread locked, so I will just recommend an entire system (all 4 corners) and not to match it with drums or stock calipers etc.. or some other brands

And so on!

JohnZ

You don't need ANY new/additional valving of any kind (proportioning or metering) to just add a dual master cylinder. What you DO need is a dual master cylinder for MANUAL DRUM BRAKES, with Residual Pressure Valves in each outlet (most are disc/drum, and you don't want one of those).

TCracingCA

Yes hot rod guys are big on Residual Pressure Valves but those don't come in most generic kit or when buying stock Corvette components. Those are really good when you are like mounting an MC low in a chassis. They usually come in drum pressures or disc pressure! But a proportioning valve can still be good for tuning to the back if you don't run some type of line pressure limiter or restricter.