I have a 71 Chevelle with Power Drum Brakes. Im going to do a frame off restoration and im going to install front and rear disc brakes but want to know will i need one of those wilwood rotary adjustable proportion valves for my rear brakes. Because i heard that you can have to much pressure going to the back to were your back brakes will grab harder than your front.

This is exactly what I'm doing on my 70. The only thing you get to reuse is the power booster. You need a new master cylinder and proportioning/metering valve. You can use the adjustable proportioning vave to fine tune it but I've been told it's optional. :cool:

Zefhix i thought i could use my master cylinder because i was told as long as it a dual bowl not a single you can use the master cylinder and what about the old metering valve well i think its a metering valve what is the thing that on the frame that all the brake lines runs to and it has a wire running from it i thought that is a metering/proportioning valve.

Actually I stand corrected. I didn't read the first time that you were drum all the way around. Disc frnt/drum rear cars (like my 70) have some sort of residual valve built into the MC that impairs the use of 4 wheel discs. You might be okay with yours. I would search this section as well as the archives to be certain. I was told that thing on the frame was merely a distribution block and a warning light for low pressure for mine....not sure if your 71 is the same. Pics?

Here is another option to consider. I was going to do the 4 wheel discs so I called Master Power Brakes to talk to them about their kits. By the time I got done talking to their tech guy I decided to go with their rear drum upgrade. They sell a rear kit with 11"x2" drums and "matrix ceramic" shoes. Everything is new from the backing plates out. Also it is much cheaper than the disc setup. In most applications the stopping power generated is in the same neighborhood as discs. In general the tech guy indicated that rear discs can be a bit of a pain to get set up right. I went with the Hotchkis tubular A-arms and 12" disc kit that Hotchkis sells and the drums from Master Power Brakes. I can't tell you what master cylinder to use becausemy car was already a disc brake car so I got to keep mine. It stops great. Look at www.mpbrakes.com (http://www.mpbrakes.com) .

I converted manual drum brakes to 4-wheel disc, and I'm using the stock drum brake metering block with no other proportioning valve or anything. I also have Hydroboost, and Paul at Hydroboost recommended running it this way. The car stops perfectly, no sign of a bias to the rear tires. I have yet to lock the tires, and I've done some very hard braking with this setup!
BTW my rear discs cost a total of about $225 including new rotors and pads...got them off a '95 camaro Z28, and they literally bolted right up.