Brake Line Size????

Have a 54 chevy truck with drums all around, didnt like the idea of a single line master cylinder so I put a dual line with a booster from a 05 Monte Carlo on it. Now that the new lines are on and the sytem is bleed the shoes are not moving much-shoes are on with new cylinders, drums are off- Any clues as to the problem-Thought that the brake line size may have to be bigger, hope not though....thanks

 

Line size makes NO difference, it is merely to carry fluid. The MC pushes a certain amount of fluid out and the same amount of fluid enters the wheel cylinders. If the shoes aren't moving, I think you still have some air, or you push rod from the pedal to the MC needs some adjusting.

 

If line size made NO difference why would 3/16 line give you a pressure increase over 1/4 inch line? Same amount of fluid pushed through a smaller opening, restriction = pressure increase.

 

You need to check bore size, also your 05 Monte master is more then likely build with disk brake residual valves. Meaning they will push 2 lbs of pressure, when your drums require 10 lbs.

3/16 should be fine.

 

you need a m/c from a drum drum system,,,, 70 montecarlo drum drum would probably suit you better.

 

It will give you a volume increase- not a pressure increase.

 

3/16 is just fine


you have other issues

 

Residual valves have nothing to do with the pressure supplied to the brakes. They maintain the specified amount of residual pressure at the wheels when the brake is released, to keep the fluid from all returning to the master cylinder and letting the pads move too far away from the rotor. They are only needed when the master cylinder is mounted below the wheel cylinders as in an under floor mounting location. Firewall mount does not need residual valves.

 

I agree

 

The ONLY things that increase the pressure in a braking system are:

Force applied at pedal.
Force applied by boost assist.
Higher pedal ratio.
Smaller master cylinder bore size.

 

You need to check that the master is getting a full stroke. If it is, and you are still not getting enough travel at the shoes than you will have to check the bore size. It needs to be pretty close to the OE master.

 

Better yet, I always try to get the donor part as close to matching the vehicle its going into. In a '54 truck, I'd be looking at a '67 or so Chevy C10 master. Truck brakes are balanced differently than a passenger car.

Bob

 

This is what you want to listen to.

Some may think that line size makes no difference. But, line size, master cylinder & wheel cylinders are DESIGNED to work as a SYSTEM.

 

Put the drums on before bleeding

 

Are you using a non power m/cyl ? Those have a deeper pushrod hole, giving the same effect as a "too short" pushrod....Power m/cyl have a shallow pushrod hole....because there is a "guide" at the booster....

From experience...... 4TTRUK

 

Just the opposite on all I've ever worked on or seen. Generally, power masters have to have a deep push rod bore because the booster push rod cannot be retained, like in manual masters. There may be some boosters that have guided push rods, but that's not the norm.
However, it's good advice to be sure the master you use has a deep bore when used on a custom manual system. You don't want the push rod to be able to fall out of the bore.

 

are you using the stock pedal? you need to measure the stroke (or movement) of the rod. i have had to lengthen the little tab on the pedal that the clevis hooks to, to get more stroke. it would be a good place to start.

 

srs1 - you hit the nail on da head - didnt have a long enough stroke

 

Don't feel bad, dude. It is a common problem.