How to Install Wilwood’s Drum-to-Disc and Tandem Master Cylinder Kit

1963 Corvette Disc Brake Upgrade Part 2

By Ron Ceridono   –   Photography by the Author

Missed Part One? See it here: 1963 Corvette Disc Brake Upgrade

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It’s been said that three of the biggest lies ever told are: “the check’s in the mail,” “this will hurt me more than you,” and “I’m from the government and I’m here to help.” Most performance enthusiasts would probably agree that the third one is the most applicable to our interests, after all the government hasn’t done many things to help the cause of hot rodding. However, there is arguably one example of the powers that be doing something useful and that was the implementation of Federal Motor Vehicle Safety Standard 105 that required all passenger cars have dual master cylinders as of January 1, 1968 (all domestic manufacturers got a head start and began installing them in 1967). The obvious value of a dual-circuit master cylinder is that the brake system is divided in half, so in the event of a major hydraulic leak, half the system would still work—some brakes are better than none.

002 The new front brakes used are Wilwood’s forged Dynalite M calipers
The new front brakes used are Wilwood’s forged Dynalite-M calipers (suffix M stands for machined, meaning the outer body is stepped to clear stock steel wheels) and 11.50-inch vented rotors.

Part 1: 1963 Corvette Disc Brake Upgrade

In the Apr. ’24 issue of All Chevy Performance magazine, we detailed the improved stopping power of a ’63 Corvette with a front disc brake kit from Wilwood Disc Brakes.

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We installed one of their Classic Series Dynalite front disc brake kits (PN 140-14663-R) that fits ’55-64 fullsize Chevrolets as well as ’63 and ’64 Corvettes. It comes with large 11.50-inch rotors, forged Dynalite-M calipers, caliper mounting brackets, hardware, and complete bearing kits. It also includes a new Wilwood Compact Tandem master cylinder to replace our stock single-reservoir unit.

003 In stock form most Chevrolets including Corvettes prior to 1967 used single reservoirsingle outlet master cylinders
In stock form most Chevrolets, including Corvettes prior to 1967, used single-reservoir/single-outlet master cylinders. Lose a brake line and the brakes are gone.

Wilwood’s Compact Tandem Master Cylinder is available in two finishes, ball burnished and black e-coat, while bore sizes range from 7/8 through 1-1/8 inches. We elected to eliminate the vacuum booster and go with manual brakes. Wilwood’s Mike Hamrick explained our options: “We only offer two manual brake master cylinders for these cars; 7/8 inch would be best for the customer going disc/disc and 15/16 inch for those who are adding disc brakes to the front and staying with drum brakes out back.”

As we stayed with the factory brakes in the rear, we followed Hamrick’s advice and went with the larger 15/16-inch bore master cylinder (PN 260-14958-BK; BK is for black e-coat). When installing the master cylinder, Hamrick recommends leaving up to 0.125 inch of free play in the pushrod, enough so the master cylinder’s piston fully returns when the pedal is not depressed.

004 Our Corvette was originally equipped with power brakes
Our Corvette was originally equipped with power brakes, which we have eliminated. Note how the brackets mount the booster at an angle.

In the process of updating brake systems, it’s common to include residual pressure valves (RPV). They’re normally available in 2- and 10-psi ratings. Their purpose is to keep brake fluid from draining back to the master cylinder reservoir, which can cause excessive brake pedal travel until the system is “pumped up” and filled with fluid again.

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Hamrick’s rule of thumb is if the system has front and rear disc brakes with the master cylinder higher than the calipers, an RPV is not needed. If it’s disc/disc system with the master cylinder under the floor, a 2-pound RPV is needed in each line. On the other hand, anytime you use drum brakes, a 10-psi RPV must be installed regardless of the master cylinder’s location. Hamrick adds that RPVs should be as close to the master cylinder outlets to hold as much fluid as possible. In our case, we installed a 10-psi RPV in the rear line only.

005 Wilwood’s Compact Tandem master cylinder is unique in that it has outlets on both sides
Wilwood’s Compact Tandem master cylinder is unique in that it has outlets on both sides and comes with fittings to allow the use of 3/16- or ¼-inch inverted flare brake lines

Another common addition to a performance brake system is an adjustable proportioning valve typically plumbed into the rear brake line. With a typical tandem master cylinder, the amount of brake line pressure delivered to each outlet will always be the same without a proportioning valve. However, since rear wheels don’t have as much traction (in a stop), and rear brakes don’t do as much, a proportioning valve provides a way to adjust that pressure.

006 the supplied plugs were installed in the unused outlets
As we used the outlets facing to the left side of the car, the supplied plugs were installed in the unused outlets.

Read More: Installing a Flaming River Steering Column in a TKX-Swapped 1969 Nova

The name “proportioning valve” seems to confuse people. The valve is more of a pressure regulator, decreasing how much pressure goes through it by a set amount (once initial pressure reaches a certain point). Reducing the force going to one circuit doesn’t increase the force going to the other brake circuit, however, when the valve reduces pressure to one circuit, the proportional relationship between the front and rear braking (front to rear brake bias) changes. The adjusting knob is marked with an arrow indicating the direction required to decrease line pressure to the calipers. The knob rotated all the way out (counterclockwise) will provide a maximum pressure reduction of 57 percent. Rotating the knob clockwise will incrementally increase line pressure up to full pressure. Proportioning valves can be located anywhere between the master cylinder outlet (but after an RPV) and the rear brakes.

007 Wilwood’s master cylinders are available in a variety of bore sizes
Wilwood’s master cylinders are available in a variety of bore sizes. For a simple and clean installation, they also offer a kit that has lines and a bracket that mount a proportioning valve to the master cylinder.

When installing new brake lines one of the common questions is what size line should be used; the common sizes are 3/16 and ¼ inch. While some think line size has something to do with system pressure, it doesn’t. However, Hamrick tells us that the smaller line size helps build psi easier, so he recommends the use of 3/16-inch line, however if a car having the lines replaced came with ¼-inch lines use that.

008 With the lid off it’s obvious that one reservoir of the master cylinder is larger than the other
With the lid off it’s obvious that one reservoir of the master cylinder is larger than the other. In this case the larger front section supplies the front brakes.

Another common brake system question is what type of brake line material to use, the most common are steel and stainless steel—pure copper line should never be used. However, there is a third option that is becoming popular: copper/nickel brake lines commonly referred to as NiCopp. This material is DOT approved and is extremely strong, with higher bursting strength than steel or stainless steel. In addition, NiCopp is easy to bend, can be flared easily, and is corrosion resistant.

009 Note the two holes in the brake pedal arm
Note the two holes in the brake pedal arm—the upper increases the pedal ratio and is for manual brakes, the lower hole is for power brakes with the angled booster (arrow). The reduced ratio was supposed to make the power brakes a little less touchy.

The last step of a brake installation is bleeding the system. Wilwood recommends bench bleeding the master cylinder. Then with the master cylinder installed, begin by bleeding the brake farthest from the master cylinder, then work your way to the brake closest to the master cylinder. With a hose connected to the bleeder screw on the caliper/wheel cylinder and the other end in a bleed bottle, have an assistant pump the brake pedal, then hold it, loosen the bleed screw, and let out the air and fluid, then close it. Do this until no more air bubbles appear. If this is being done without help, submerge the hose in the bleed bottle partially filled with clean brake fluid, then loosen the screw and pump the brake pedal until no bubbles are visible. When bleeding brakes, monitor the fluid level in the master cylinder. If it has emptied the system, it will be filled with air and the procedure will have to be repeated.

10 we installed a Wilwood (PN 260 8419) adjustable proportioning valve
To allow balancing the front-to-rear brake bias, we installed a Wilwood (PN 260-8419) adjustable proportioning valve.

Read More: The Ongoing Evolution of Drag Racing Tires

After installing new brake components and bleeding the system, Wilwood recommends bedding in new brake pads as follows: After testing the brake system at low speeds to determine if the vehicle is safe to operate, in an area where it’s safe to proceed, begin with a series of light decelerations to gradually build some heat in the brakes. Use an on-and-off pedal technique by applying the brakes for 3-5 seconds and then allow them to fully release for a period roughly twice as long as the deceleration cycle. If you use a 5 count during the deceleration interval, use a 10 count during the release to allow the heat to sink into the pads and rotors.

11 Due to the Corvette’s recessed mounting position of the master cylinder
Due to the Corvette’s recessed mounting position of the master cylinder, a side-mounted proportioning valve wouldn’t fit so we simply bolted it to the firewall.

After several cycles of light stops to begin warming the brakes, proceed with a series of medium to firm deceleration stops to continue raising the temperature level in the brakes.

Finish the bedding cycle with a series of 8-10 hard decelerations from 55-65 mph down to 25 mph while allowing a proportionate release and heat-sinking interval between each stop (20-30 seconds). The pads should now be providing a positive and consistent response.

12 Due to the Corvette’s recessed mounting position of the master cylinder
We used Wilwood’s universal flex brake line kit (PN 220-7699). It includes 16-inch, -3 AN, 3/16-inch hoses; AN to inverted flare adapters; brake line retainers; and 90-degree caliper fittings.

If any amount of brake fade is observed during the bed-in cycle, immediately begin the cooldown cycle. Drive at a moderate cruising speed, with the least amount of brake contact possible, until most of the heat has dissipated from the brakes. Avoid sitting stopped with the brake pedal depressed and do not apply the parking brake. Park the vehicle and allow the brakes to cool to ambient air temperature and you’re done.

13 Wilwood recommends wrapping the pipe thread portions of the caliper fittings with Teflon tape
Wilwood recommends wrapping the pipe thread portions of the caliper fittings with Teflon tape. The excess will be cut off after installation.

Our Corvette not only has better brakes with discs up front, but it has the safety benefit of a tandem master cylinder. The good news is the same thing can be done to just about any drum brake–equipped Chevrolet. The bad news is it ruins a perfectly good joke about the government.

14 It’s critical that the brake hoses be routed so as not to contact the suspension as the wheels turn
It’s critical that the brake hoses be routed so as not to contact the suspension as the wheels turn.
15 On the frame end the AN to inverted flare adapters allow the braided hoses to connect to the factory steel brake lines
On the frame end, the AN-to-inverted flare adapters allow the braided hoses to connect to the factory steel brake lines.
16 Included in the Wilwood brake line kit are spring clips that secure the hose adapter to the bracket on the chassis
Included in the Wilwood brake line kit are spring clips that secure the hose adapter to the bracket on the chassis.
17 Wilwood’s DOT 5 1 brake fluid has a 570 degree boiling point and is resistant to aeration and foaming
Wilwood’s DOT 5.1 brake fluid has a 570-degree boiling point and is resistant to aeration and foaming, which all means improved pedal feel in severe use.
18 Before installation master cylinders should always be bench bled with the supplied hoses and adapters
Before installation, master cylinders should always be bench bled with the supplied hoses and adapters. We chose to do it with the master cylinder installed before the lines were connected.
19 The master cylinder lid gasket serves two purposes
The master cylinder lid gasket serves two purposes: it prevents fluid leaks and prohibits the fluid from becoming contaminated by dirt and moisture.
20 To add the brake lines necessary for the tandem master cylinder
To add the brake lines necessary for the tandem master cylinder, we used 3/16-inch NiCopp (nickel/copper) tubing from Speedway Motors. A 25-foot roll (PN 91095101) comes with tube nuts and line clamps.
21 It’s important to secure brake lines to prevent chaffing against the chassis from vibration
It’s important to secure brake lines to prevent chaffing against the chassis from vibration. We used these simple clamps from Speedway Motors (PN 91031315-3/16).
22 Steel and NiCopp brake lines must have 45 degree double flares at connection points
Steel and NiCopp brake lines must have 45-degree, double flares at connection points. This tool from Speedway Motors (PN 91031837) forms 45-degree double-, single- and bubble flares in 3/16-, ¼-, 5/16-, and 3/8-inch diameter lines.
23 This is a 45 degree double flare Note how the flare is folded back onto itself
This is a 45-degree, double flare. Note how the flare is folded back onto itself. By comparison, stainless steel lines use 37-degree single flares.
24 The new rear NiCopp brake line has a 10 psi residual pressure valve between the master cylinder and the proportioning valve
The new rear NiCopp brake line has a 10-psi residual pressure valve between the master cylinder and the proportioning valve.
25 To separate the brake lines fore and aft a new front brake line from the master cylinder was formed
To separate the brake lines fore and aft, a new front brake line from the master cylinder was formed. It connects to T-fitting 26 with a mounting bracket (Speedway PN 91031837) that feeds both front calipers.
26 The new front brake line attaches to the front outlet of the master cylinder
The new front brake line attaches to the front outlet of the master cylinder. It runs down to the front framerail to keep it out of harm’s way.
27 Like many cars C2 Corvettes have some brake lines with complicated bends
Like many cars, C2 Corvettes have some brake lines with complicated bends. To make life easy, we ordered these rear brake lines (PN 500123) for our ’63 from Keen Corvette Parts.
28 With everything plumbed the last step in the installation of the new brake system was to bleed the brakes
With everything plumbed, the last step in the installation of the new brake system was to bleed the brakes. Wilwood included a brake bleed bottle with our brake kit.

Sources:

Keen Corvette Parts
(800) 757-5336
keenparts.com

Speedway Motors
(855) 313-9173
speedwaymotors.com

Wilwood Disc Brakes
(805) 388-1188
wilwood.com

Click on this issue’s cover to see the enhanced digital version of How to Install Wilwood’s Drum-to-Disc and Tandem Master Cylinder Kit.acp may 2024

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