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I was in the process of replacing the master cylinder on my recently purchased ‘61 Dynamic 88. The car had been stored for well over 10 years and as a result the master cylinder was seized. I was planning on replacing the single pot with a new single pot, making sure the emergency brake functions and inspect all components...... but while I’m doing a master cylinder replacement, I couldn’t help but think I should just install a dual reservoir master cylinder for safety.
I ended up picking up a booster and master cylinder from a ‘65 Cadillac. The ‘65 booster had 3-1/2” of pedal arm, just as my original booster had and the master cylinder was for a drum/drum brake system. The mounting bolt spacing was the same top to bottom but the new booster mounting bolts side to side were 1/2” wider. I hogged out the holes on the firewall plate (not very neatly as I was using a buddies drill press and the bit would wander as I was drilling through the plate as I was only taking away a 1/4” of material on each hole)....... but it did work, and once bolted in place you can’t see it anyway.
Once bolted to the firewall, the plate acted as a template to clean up the firewall with a dremel. The brake pedal also needed slots cut in the lower mounting holes. I removed the pedal and a Zip disk made short work of the cutting.
Cleaned up the booster and master cylinder and mounted them.
I reused the brake line splitter block, plugging the port for the rear line and then using a coupler and a 12” line to tie the rear lines to the rear brake port of the master cylinder. A new 12” brake line tied the front brake block to the master cylinder.
The master cylinder has 1/2” ports so I needed to use reducing couplings for the brake lines at the master cylinder which you can see here. The existing vacuum lines weren’t touched. I added a plastic 3/8” tee and tied the new booster into the vacuum system with a short piece of fuel line.
All in all a fairly painless conversion and now don’t have to worry about a catastrophic brake failure. I’m really happy with the “look” of this install vs. an aftermarket dual reservoir and booster conversion.
Hopefully this helps someone else.
Allan
Did you have any problem with pedal ratio? I did a dual swap on my 63 Dynamic recently. I used a 66 (or so) corvette style Master Cylinder, and when I mounted MC and booster in the stock position I couldn't get enough pressure from the pedal due to incorrect pedal ratio. After a lot of trial and error, I wound up using a 65 single diaphragm booster and modified a relocation plate from speedway that raised my booster and MC about 2.5 inches. I went from 2.7:1 to a little over 5.5:1 and my car stops great now.
