I HAVE A 67 FIREBIRD WITH DISK UP FRONT[4 PISTON CALIPERS]AND DRUM OUT BACK. I JUST PUT ALL NEW BRAKES LINES-CALPERS-ROTORS-NEW POWER BOOSTER[FOR DISK WHICH I DIDNT HAVE BEFORE] -WHEEL CYLINDERS-AND NEW PADS.. MY QUESTON IS WHAT CAN I DO ABOUT THE PROPORTION VALVE AND METERING VALVE?MINE ARE STUCK.AND I CANT FIND A NEW ONE?IS THERE ANYTHING ELES I CAN USE AND HOW DO I HOOK IT UP? THANKS MIKE0861@AOL.COM
If your car was drum brakes and you converted to disc, let me help shed some light on the problem. Drum brakes didn't use a portportioning valve. Instead, that's a brake light switch.
I think that an adustable porportioning valve would be the only way to go. Unless someone can offer a better soution or know of a referecne, I'd adjust it, using hit-or-miss adjustments, before I'd consider allowing a professional to adjust it.
to clarify; the distribution block can be replaced by a combo valve, but it will not be set up to your specific application.
an adjustable prop valve can be set to compensate for your center of gravity, which can change due to ride height (which can change with a tire change), and spring rate. you can also adjust it to your friction material (or lockup point, which also can change with tires). basically, tighten it untill the rears lock up first, and then loosen it untill they dont.
a proportioning valve is definitely desired.
the hold off (metering) valve is not really necessary on our cars, unless you feel it nosedives too much. it really was added due to complaints of the rear end sliding out during stoplights in snowy conditions. the OE metering valve holds off pressure to the rear brakes until 30 psi is reached, so little old ladies dont have to keep their foot so hard in the brake while stopped at a light in the snow. but it can also prevent nosedive on initial application.
a combo valve would include metering, distribution, proportioning, and the brake light switch, but is not adjustable. it would be put in place of the distribution block, and no other valving would be needed. unfortunately, it is not adjustable to your cars needs.
actually, i am looking for a manufacturer of prop valves who will provide information on different 'knee points'. the 'knee point' is the point at which the front and the rear change the amount of pressure they recieve. the adjustable valves i have seen do not provide this info. typically, the front and rear recieve the same pressure until the 'knee point' is acheived (around 250psi in many cases) and then reduces by a percentage. the percentage is adjustable, but i dont know that the 'knee point' is. maybe it adjusts too. i am just unhappy with the description of any adjustable valve i have seen.
i will still get one for my car, and adjust it as i described.
