Adding Vacuum Assist for Power Brakes
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This is what you need to fix a low vacuum condition to give about 20" Hg vacuum for power brakes to be effective. My idling vacuum is 12.5", and the power brakes still required a fair amount of pressure to stop the car .......Upper left is a GM style vacuum pump with the suction port connected to a check valve then to a tee that branches off to a vacuum reservoir, then to another tee with one port going to a vacuum control switch and the other port going to the power brake diaphragm. The discharge port from the vacuum pump (smaller line on the pump) should tie into the original connection on the carburetor. Made a mounting plate to put it near the firewall on passenger side "under edge of fender". Painted black after this pic. As an additional note, a power brake booster is a safety issue that should not be ignored. Think of what happens if for some crazy reason your engine dies while you are going kinda fast or approaching an intersection. In addition, the vacuum storage canister is needed because when you press the brake pedal, the vacuum is immediately depleted and the pump comes on, but if it can't keep up with the vacuum demand, you lose your vacuum assist and you have to cram on your pedal to apply your brakes. The canister gives you some "reserve vacuum".
This is the vacuum control switch (from Amazon) that's actually made for shifting problems on automatic transmissions. The only problem with this switch is that there is no differential adjustment (vacuum difference between opening and closing, When used without a vacuum reservoir, it short cycles about 10 times before it settles down and stops cycling the vacuum pump. This switch as shipped is adjusted for 5" or 6" of vacuum for kickdown shifting, so I randomly screwed the adjustment clockwise two revolutions, and it now opens/closes at about 20" Hg.
Closer view of vacuum switch connections. This wire goes to the vacuum pump hot (red) and the normally closed terminal is connected to Accessory power (add a 10A fuse) and the other wire from the normally closed feeds the vacuum pump. The second wire from the vacuum pump goes to ground.
These are all over the place on Amazon, It will not hold it's own vacuum when it is de-energized. So a check valve is necessary to hold the vacuum on the control switch. This tube is the discharge tube that should be connected to the carb. This contributes to minimal run time, since the pump only has to pull (20" minus 12.5" equals 7.5" of vacuum). I read somewhere that one should install a filter in this line to the carb. I can only guess that recommendation is so in case the vacuum pump destroys itself it won't throw debris into the engine. Might be a good idea. hahah
The GM label on the other side of the vacuum pump. The pump has built-in rubber isolation mounts, but I mounted the two isolated screw mounts on a plate which in turn is mounted with one screw on the end of a plate that also acts as a ground connection, and a foam insulating pad (leftover from the underhood insulation pad) stuck to the bottom of the plate where it contacts some wires inside the fender well. The pump is apparently a vane type, as the sound is a whine.
