Steve's Camaro Parts - Converting Drums to Discs

Use a single piston caliper and rotor for a 69 Camaro or from my list of donor cars, they are all single piston.

You need a caliper mounting bracket, brake hoses, pads, bearings. You don't need the two piece rotor and hub like the origonal 69 used. The Monte and Nova used a one piece cast hub and rotor.

67 thru 68 Camaro used 4 piston calipers and the two piece rotor. I've heard there may be caliper to rotor clearance problems with the one piece rotor and 4 piston calipers on these cars. But the single piston calipers work fine,

Your drum booster should work, use a disc brake master cylinder. Get a 1970 or newer one piece combination brake valve and mount it under your master cyl. Take off your old brake warning switch, replace with the Combination valve.

NOTE: front disc brake Camaros from 67-69 used three separate valves for:

  1. 1. metering (hold back)
  2. 2. F/R pressure differential warning (Used on some disc and some drum brake Camaros, usually on front-heavy models like BB engine and AC cars.
  3. 3. proportioning.

The "combination" valve contains all these funcitons for a 1970 and later Disc/drum brake car. For use with four wheel discs, an adjustable rear proportioning valve may or may not be needed.

The brown brake light warning wire plugs into the combination valve.

The combination valve has four functions:

1. Metering - holds back pressure to the discs until 40 psi is reached, so the rear brakes can overcome the return spinings and take up slack. Keeps front from grabbing under VERY LOW PEDAL PRESSURES ONLY, LIKE WHEN YOU ARE ON ICE OR VERY SLIPPERY SURFACES. Once you are over 40 psi line pressure there is no benefit to having this valve.

2. PRESSURE DIFFERENTIAL WARNING SWITCH -same as drum, senses differences in front to rear pressure, warns of leak by turning on a brake warning light on the dash.

3. PROPORTIONING- reduces rear pressure to balance front to rear traction. fronts should lock first.


A stock front disc 67-69 Camaro uses separate valves for each function above. Some do not use the proportoning valve down on the frame rail.

Many drum systems have a residual pressure valve (a little piece of rubber the size of an eraiser tip) in the master cyl outlet just behind the little brass seat where the brake line screws in. It maintains a slight (10 to 15lb) pressure to keep the wheel cyl cup seals inflated. Drum master cylinders also lack enough stroke and/or enough reservoir volume to properly operate disc brakes.

WARNING- most discs do not use a residual pressure valve (RPV). Some aftermarket disc systems use a 2lb RPV which is OK, it helps pedal height. caliper seal design is a main factor in RPV requirement.

Drum brake systems use: a brake pressure warning switch/distribution block only, with some models using a proportioning valve attached to the frame under the drivers seat area. And a RPV in the master cyl outlet.

Disc brake Camaros use: NO residual pressure valve in the disc side of the master cyl. The drum side often has a RPV. A round metering valve with rubber push button, by the master cyl, and a Proportioning valve on the frame rail. Also a brake pressure warning switch under the master.

Early Vette four wheel disc and Camaro JL8 systems use: NO RPV, NO Metering valve, they do not use a proportioning valve on the 69 Camaro JL8 four wheel disc system.

When swapping master cyls, there are at least two different length master cylinder push rods coming OUT of the booster. To fit different depth master cyls. The rod can be removed from the booster by pulling on it. It has an O ring on it. If the master cyl you get is deeper where the pushrod goes, you either have to swap the pushrod, or you can cut a length of rod or bolt and put it inside the master cyl to make it the same as the shorter drum brake master cyl. If the rod is too long you can cut it.


If the push rod is the wrong length, your brakes will lock or not work at all!

With stock calipers, use a 1 1/8" master cyl bore size master cyl on a power disc system. A 1" bore on a manual brake system. Make shure the master cyl piston returns all the way or it won't uncover the replensihment port to the reservoir.


The rear pushrod hole in the booster must be open to the air. If you are swapping to power brakes and transfering the manual brake rubber boot to the power booster. THIS WILL PREVENT THE BOOSTER FROM WORKING. There is a felt pad in the booster around the pushrod to keep noise down. That is all that should be in there. For road racing they remove the pad for faster brake actuation.

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