Installing a Master Cylinder

I'm upgrading my 54 Pontiac brakes to 4 wheel disk brakes from a 1984 Olds Toronado. I've removed the 54's original under-the-floor master cylinder plus the 10 lbs of dirt covering it. Is it just me or is it just a really bad idea to mount important mechanical components where dirt and debris can easily reach it but mechanics can't?.

The Toronado's brake pedal assembly has the brake switch attached to it, so its just a matter of mounting the whole assembly. Right off the top, it looked like there was going to be clearance problems with the gauge cluster access plate, steering shaft hole and possibly the drivers fresh air vent.


Possible clearance problems with mounting master cylinder on firewall

Master cylinder

85 Toronado master cylinder, brake pedal and proportioning valve

In order to mount the master cylinder, I cut a 5" square in the firewall right under the instrument cluster access hole and over the driver's fresh air vent (I'll have to relocate that later). The Toronado master cylinder is designed to mount to a firewall that is at about a 15-20 degree angle from vertical. I had to make an angled mounting bracket and weld it on the firewall.

master cylinder

Master cylinder and mounting bracket

The mounting bracket is silver in the pix and the firewall is green. I've tried to get the brake fluid reservoirs level. May have to add some washers for fine adjustment but I won't know until the car is back on the ground. I filled in the firewall's triangular shaped support hole right under the fresh air vent and will be mounting the proportioning valve there.

Master cylinder

Master Cylinder and proportioning valve

Sorry for the quality of pix, my scanner seems to be dying after 5 years. I welded up the triangular firewall openning and mounted the proportioning valve right under the master cylinder. Just a note, the brake failure switch is mounted in the up position. Don't really know if this would make a difference since its all hydraulics but best to leave it in the factory position. The curls of brake line are to match the OEM installation - probably for cooling.

I had to bend the brake pedal lever so that it would sit at the correct position. I cut a knotch in the lever arm, bent the pedal so that the knotch was closed and welded it.

brake pedal

Looking under the dash at the brake pedal assembly

When I bled the brakes, I found that the master cylinder and firewall flexed a little - not much but just enought to bother me. I don't like safety items like master cylinders to flex. So I made a little brace out of some 2" wide 1/8" flat steel stock and bolted the top of the brake pedal assembly to the top of the firewall. Now there is absolutely no flexing and I'm happy.

brake brace

Brace connected between top of firewall and brake pedal assembly

You can't see it in the pictures but there is a mounting flange on the top of the Toronado's brake pedal assembly for bracing it. Unfortunately, the bolt hole is about 13/16" in diameter. I thought that I put a washer in the bolt hole and sandwich the mounting flange with larger washers. I couldn't find a flat washer that worked but did find that a 3/8" lock washer is the perfect size. So the lock washer acted as a "reducer" and I added a couple of large 3/8" id flat washers and bolted everything up.

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Copyright July, 2011 Eugene Blanchard