Hello guys, im new to the classic car world and need some help. I have wrenched on Harleys and 4x4's and now have joined into the classic car realm. I have purchased a front disk brake conversion kit to install on my 54 bel air and keeping the rear drum. I have also purchased a dual master cylinder for a late 60's model truck that Im going to fabricate to fit my car back in the stock location (thanks to the wonderful thread posted about how to do it). I really dont know much about brakes and need some pointers on how to make the disk/drum brake conversion work with manual brakes. Here are my questions...Will I need to install a proportioning valve? I know after reading a thread a minute ago that I will need a residual pressure valve for the front disk, but will I also need one for the rear drum? And where do they exactly go? Are they plumbed inline before the split? If you have any answers or pointers to make my conversion go smoother due to past experience please let me know. I greatly appreciate it!
Where in Tennessee are you? Here's my take on your setup... Your plumbing goes from the master cylinder, to the distribution/proportioning valve, then to the front/rear residual valves, on to the front and rear unions, then to the calipers/wheel cylinders. The distribution block and/or proportioning valve direct the proper amount (proportion) of fluid to the front and back. Disc brake calipers have much more volume than the wheel cylinders, so this valve helps distribute the fluid properly. The residual pressure valves keep they system kind of pre-loads your brakes (overcoming the pressure from the brake return springs) to keep you from having excess pedal travel. The springs on drum brakes are much stiffer, so they usually require about a 10 lb. valve. Discs have little or no spring pressure so you'll only need about a 2 lb. valve. If the master cylinder is mounted up on the firewall you won't even need one for the front brakes - gravity will do the trick. Your brakes will probably work okaywithout proportioning and residual valves, but then again your drum brakes probably would have worked okay as they were. In my opinion if you're gonna spend all that money on disc brakes spend a few bucks more and do it right.
Normally, yes, because disc brakes require higher pressures than drums, and proportioning valves limit rear pressure (not volume) to prevent the rears from locking before the fronts discs. An adjustable P/V is always a better option vs. a factory or after market fixed value prop valve. [/QUOTE] I know after reading a thread a minute ago that I will need a residual pressure valve for the front disk, but will I also need one for the rear drum? And where do they exactly go? Are they plumbed inline before the split? [/QUOTE] All pre-'70s drum brakes require residuals, to prevent air from entering the wheel cylinders during fast brake release. The late '60s master you have should have a built in residual in the rear port, assuming (?) it's a disc/drum master, and if missing, use a 10 lb external valve to the drums. (Use either a disc/drum or disc/disc master) A 2 lb after market residual is needed for disc brakes ONLY when the master is located below the floor, or calipers, and all residuals should be located close to the master outlet port(s)
Thanks for the responses guys, located in Chattanooga. I just bought an adjustable proportioning valve that came with 2lb and 10lb residual valves. I hope to have everything ready to pop them in by the weekend. Just got to put on my disk brakes and all the bearings and what not on and get some brake lines and get them bent and put in.
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