Brake Question

[zooming993]

I’m working on my 70 El Camino with factory disc brakes up front and drums in the rear. I’m in the process of replacing the master cylinder along with the booster. The prior owner installed an adjustable proportioning valve, which I will be replacing with a CPP (PV4) proportioning valve. I bought the PV4 because I’m also installing a CPP rear disc brake conversion kit. My question has to do with the factory distribution valve mounted to the frame. Does the PV4 valve replace the distribution valve or do I need them both?

[shadowgray396]

It replaces the factory distribution block on the frame. Also since this is a '70 that you are working on that had rear drums brakes there may be a pressure hold back valve mounted back by the inside frame rail on the rear frame. Not sure on the Elkys if they had them, but 70 Chevelle had one hidden back there. GM did away with it with the combo valve used in model year '71 and up.

[zooming993]

Thank you for all the replies. I’m beginning to think this is going to be a bigger job then I planned. I understand the new proportioning valve (PV4) will replace the original distribution block mounted on the frame. As for the pressure hold back valve some have mentioned, I found it, it’s mounted on the drivers side above the axle tube. I’m assuming this valve needs to be removed when I install the rear disc brake conversion, correct? If it does need to be removed can I replace it with a threaded coupler or do I need to replace the entire brake line?

Thanks again for all your help.

[shadowgray396]

The pressure hold back valve will not be needed for 4 wheel disc brakes set up. Coupler will work, I like the least amount of fitting on brake lines, less chance of a leak.

[bafflefinder]

Along these lines, just bought a72 malibu and the rear drums were a mess. I replaced them with discs so discs on front and rear. I also replaced the master cylinder. I bled the master but can't bleed the system. I have 1/2" free pedal before the rod depresses so I am sure I am getting full rod release at the master. I believe I have to replace the proportional valve with a distribution valve since the rear discs don't have a spring to overcome. Is this correct and is this all I have to do?