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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
Last edited by Al T; February 7th, 2021 at 03:41 PM.
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.
February 7th, 2021, 02:14 PM
