Question - What is correct complete system we should have ?- we were told different answers on our Drum/ Drum I'll list what we have AND Our Question We have; SBC 305 Motor * Fire wall mounted Corvette Style Dual Master 1" bore ( in case future convert to disc) 7" Booster & also we mounted a Vacuum Canister * 53 Chevy Front Drum Brakes * 66 Chevelle Rear and Drum Brakes Question What size Residual Valve should we use ? 2lb or 10lb Should we install over rear housing a " Porportioning Valve - is it needed or just a regular " T " fitting
You want to use 10# residuals for your older drum brakes, regardless of master cylinder location. I would pitch the 7" booster unless it's a dual diaphragm-better to go 8" or larger. Drum systems never used proportioning, but wheel cylinder re-sizing may be required for the non-stock rear axle.
don't need a proportioning valve. put the 10 llb residual valves as close to the master as you can. I have pretty much the same set up on my 51 Chevy, 7 inch dual diaphragm booster, and it works great.
Questions - When you 10lb valves (plural) we were told only one needed going to rear brakes. Not front brakes * Also we have 305 motor and it seems no way enough vacuum even vacume canaster so we might go 8" what motor do you have?
I also think with a drum/drum you only need a small master with residual valves built into the master outlets only, save the vette for when you change over.
You need them to all the brakes. If you use a master that has them built it, the you dont need them, but if using the Vette type master, I am, you need them. How much vacuum are you pulling on your motor? Unless it is just slam worn out or has some giant cam in it you should be able to pull enough vacuum to operate power brakes. I have a bone stock 290 horse gm 350 crate motor and it pulls 19 to 20 inches of vacuum for days. A booster that is too small will feel like you dont have enough vacuum to operate it also.
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