Hard Stopping

[jim]

I replaced the small manual brakes on my a body with disc on front and 2 1/2 bands on the rear. I had a good hard peddle but was hard to stop. The car stopped better with the old system. Added a power booster but still have the same problem and the brakes seem to release slower. I had changed the proportion valve which is suppose to be off a power disc car. Any info would be helpful.

 

[RedFish]

The master cylinder as well as perportion valve, and vacuum booster should all be correct components for power brakes. Mix and match or used (part yard) stuff will only cause problems.
Many performance cams wont create enough vacuum for power boosters to operate properly. Dunno if any of this helps.
I will add that if your original brakes were those 9X3 , slant 6 drums... thats a whole bunch of braking surface that you no longer have. The main advantage of front discs is straight line braking in a panic stop situation rather than shorter distance braking.

 

[jim]

Thanks, Mastercyl is new for power disc,has good vacuum. How does a person identify the type of proportion valve?

 

[RedFish]

Thanks, Mastercyl is new for power disc,has good vacuum. How does a person identify the type of proportion valve?

Beyond part numbers, I dont know. May be physical differences but I doubt it. Hope someone else chimes in with more help. Meanwhile you could double check the line routing from master cylinder to front and rear wheels. Look for kinked metal lines and or clogged flexible lines. I have a 73 here with OEM front power discs and could get some pics later (its raining now) which might help. Good luck

 

[NiceFishEh]

Beyond part numbers, I dont know. May be physical differences but I doubt it. Hope someone else chimes in with more help. Meanwhile you could double check the line routing from master cylinder to front and rear wheels. Look for kinked metal lines and or clogged flexible lines. I have a 73 here with OEM front power discs and could get some pics later (its raining now) which might help. Good luck

On my 73 to 76 disc conversion on the Fish, I ordered a MC for a 75 Dart. My prop valve came out of the Dart parts car.

What I noticed was the ports on the MC and prop valve matched to accept 1/4" tlines for the front calipers and 3/16" for the rear. So thats what I did.

This will probably give me a harder peddle, but I think the larger line is for volume.

A lot of times, guys will bush down the fronts and use 3/16" all around.