Sorry no post last week, but I'll try to make up for it with this one. This is the original brake master cylinder. When you push on the brake pedal, it pushes the aptly named pushrod into the rear of the master cylinder, displacing brake fluid through the lines to the wheel brakes. This original style mc is the single chamber style, meaning that all four brakes are supplied by one common chamber simultaneously. You can see the single outlet tube that eventually splits, then each splits again for four wheels. Very simple.
This mc was adequate for the four wheel drum brakes this car came with. The only possible problem is that if any part of the system developed a leak, the entirety of the fluid could leak out in just a few pumps, leaving you literally without any brakes at all. Very scary, but usually leaks develop slowly, not where like a whole line is severed completely at once. If the whole system is rebuilt and fresh, there shouldn't be any problems. In fact I did rebuild this one and have every confidence in it.
Below is our upgrade. A dual chamber master cylinder, identifiable by the dual hump cover and the two outlet ports. The immediate improvement is that one chamber feeds the front wheels, and the other chamber feeds the rear wheels independently. Losing pressure in one circuit would still leave the other intact. This improvement came standard around 1966-ish. The mc pictured is an even later one, for front disc/ rear drum Camaros circa 1980. I'm going to change the front brakes completely over to discs, hopefully next week. Thus the need for this new mc.
I took this reverse angle shot of the brake line from the mc. If you'll notice, the brake line makes a vertical loop, likely done to absorb excess line length of a poorly-executed universal replacement line install . A cars' whole brake system is dependent on hydraulic pressure; simply fluid being pressurized, and moving through tubes. Brake systems must not have any air in them, as air will compress (fluid will not) and cause poor pedal feel and braking action. The vertical loop is likely to trap air in it during the bleeding process, since bleeding is done from the mc out and downward to each wheel. My point is this: the loop should have been done (if at all) on the horizontal instead, sweeping downward. Envision how simply rotating the loop 90* clockwise would have fixed this. A custom correct length line is the best solution of course.
Very fortunately, the new mc bolt holes align perfectly with the existing mounting studs on the car. I'm stunned that this dimension was kept uniform for at least 20+ years. Unfortunately, the existing pushrod was way too long to accomplish an easy bolt on. Some careful measuring and calculation revealed that the pushrod will have to be shortened 15/16". It's kind of hard to see below, but the pushrod is threaded into the clevis to allow some adjustment. I'll free this up, but still cut off the offending amount to get the length close. FYI, the clevis on the right attaches to the pedal arm, the other end pushes into the mc.
Here at last is the new mc in place, freshly primed and painted semi-gloss black for the factory look I like. The old line is still in place, we'll run two new lines to replace it. I reused the bulky original nuts, of course! I have an extremely strong preference for reusing original hardware whenever possible. New hardware store hardware never looks authentic, and although I'm not going for restoration quality authenticity (obviously) too many new parts add up (even cheap nuts and bolts) and kill the '60's style build theme I'm going for. If I had painted the mc bright silver, and used bright new plated nuts, the first thing anyone would notice is the new, out-of-period mc.
Below is a wider shot of the install. I really dig how the new mc's squared-off shape even mimics the boxy look of the original mc. What can I say, this sort of stuff matters to me. Excuse the grungy underhood area, we're going for function right now. Also excuse the horrific bright yellow spark plug wires, but they came with the car and they work.
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