My power brakes are soft and I have no air in the line. 4 wheel disc brakes. My brake guy said I have a 50-50 balance in the master and I need 70-30 or 60-40. The motor is a 434 stroker and in a 71 Z28. What type master would be right. New to the forum. Thanks for your help.

 

If, in the process of bleeding before, you didn’t flush all of the old fluid out of the system, do that.

If you’re sure you’ve bled all the air out and it’s all fresh fluid, but the pedal is still soft, the next thing to do is replace the flexible rubber lines at each wheel. You can replace with braided stainless lines or just get new rubber. Stainless is a little better and a lot more expensive in general; not sure about the specifics for a second-gen.

Pedal firmness is also affected by the diameter of the master cylinder (larger = firmer; it moves more hydraulic fluid for a given amount of pedal travel) and by pad/shoe material selection. A poor pad choice can cause a soft pedal.

As for the master cylinder bias, it’s not likely the cause of your soft pedal. The front-to-rear bias only matters for very hard braking. Do you drive this car on a track? Daily it in heavy traffic? By the looks of your photo, I’m guessing no. If I’m right, you’re mostly fine with 50/50.

What’s the braking setup on your car? Front discs and rear drums? On front-engine cars, the front brakes do 80+% of the work, and so you want them to get 80+% of the braking torque, but differing configurations front-to-rear make it difficult to determine the right bias.

Assuming your brakes are stock, think the best thing to do would be to find out what the OEM master was and get something that matches. If you can’t figure that out and don’t want to settle for 50/50, get an adjustable proportioning valve.

If, during a panic stop, your rear tires lock and the fronts don’t, then you have too much front bias.

You can also adjust bias with pad selection. A more aggressive pad up front will move the bias forward.