QuestionQUESTION: I'm restoring the above car. It has disc brake conversion kit put on the front. 1/4" brake lines to each brake have been installed. The brakes are operating properly....will not lock up? Hope you have a solution. Thank you.
ANSWER: Hello Wendell,
Sure they're not anti-lock brakes? Just kidding. Your cause is most likely due to the lack of, or misadjustment of the brake system proportioning valves.
Your stock drum system didn't have such a valve but disc/drum systems do.It should have been part of the kit but it's possible that it was left out as the brakes will work without it. Trace back your lines to see if they're present although most people put them close to the master cylinder because many aftermarket systems have adjustable valves in order to fit a variety of cars. The valve helps you adjust the proportion of front to back braking in order to prevent premature lockup.
Good luck on your Chevy!
Bob
---------- FOLLOW-UP ----------
QUESTION: I have placed the proportioning valve on. Now the brakes do fine when first starting out, but then it's as if pressure builds up in the lines and one of the front wheels almost locks up. Could this be from the heat of the manifold and if so, what else can I try to correct this problem. Thank you.
AnswerHello Wendell,
Good news about the proportioning valve, hopefully it's adjustable. I doubt if the exhaust manifold is involved as even if you laid a brake line directly on it, causing it to boil,(which you wouldn't), boiling brake fluid would cause bubbles and actually decrease pressure and reduce brake actuation at the wheel.
Having said that, I have had your problem before and it's sometimes difficult to track down. You see, physics tells us that fluids are self-equalizing. That means that given a common source, pressure in both front brake lines should be equal. What can make pressure unequal at the actuation point on the wheel can be many: adjustment (although disc brakes should be self-adjusting), wheel cylinder leakage on rotor or sticking on one side, rotors out of round, different brake lining materials at each wheel (it's an old car!), external or internal collapse of brake hoses, etc. etc. You've got to do a diagnostic evaluation of the system and systematically correct what you find to solve this.
Sorry, no easy answer here but a cookbook to follow. If this is more than you want to tackle, go to a reputable brake shop that has some experienced guys/gals and see what they think. They work on disc and disc/drum systems like yours every day and should have some useful insights.
Best of luck,
Bob
