Hot Rods time for a brake

my A has disc brakes in front and drums on the rear. do i need a proportioning valve if my master cyl. has two reservoirs and two lines. one line runs forward to the calipers and the other goes back to the drum brakes.
thanks
rer_239

 

Is the master cylinder on the firewall or under the floor?

 

under the floor.

 

here is the recommended set up for under the floor from Speedway motors

 

you will see 2 pound residual valves for the disc and 10 pound for the drum, along with an adjustable proportional valve

 

You must run a proportioning valve with front disks.
Maybe not with a all drum system but it is a must with disks or disk/drum.

 

ok that how i set it up, but what does the proportioning valve do? and what do the residual valves do?

 

Very simply, proportioning reduces and proportions (by percentage) line pressure to the rear brakes to prevent early rear tire slide which will result in loss of control.
Drum brake residuals (factory internal in the master cylinder or external 10 lb. aftermarket) prevent air from entering past the wheel cylinder cups during brake release. The 2lb aftermarket residual is only used with discs when the master is below floor mounted to prevent fluid drain back from the calipers.

 

So with a Drum/Drum set up I need 10psi valves on both correct?
And........Aslo I do NOT need a proportioning valve?, or I DO need one. All I find is for Disc/Drum setup. Can someone PLEASE clarify a Drum/Drum set up for me!! (My dual MC is under the floor. (no booster)

 

Residual valves were needed on older drums, but will help pedal feel on later ones, so I would install 10 lb external valves to each axle if internal valves are not present in the master you are using.
Drum/drum systems never used, and normally do not need proportioning. An exception might be modern or oversized servo rears being used with early non-servo fronts, like later Bendix duo-servo rears and '39-'48 Lockheed fronts. Tire sizes and vehicle wheel base/weight should also be considered.