Parts required for swapping manual disc to power disc??

[dustoff440]

70 Dart with factory kelsey hayes 4 piston disc front, rear 10 x 1/34 drums.
The wife won't drive it unless it has power brakes .
I'm guessing I need the following:
power brake booster
correct pushrod
correct master cylinder

what else do I need?

can I keep the original proportioning valve?

 

[slantsixdan]

Prop valve doesn't change, though you'll want to put smaller wheel cylinders in the 10" rear drum brakes to prevent the grossly premature rear lockup the disc brake A-bodies tend to have -- it's aggravated with power brakes. See here (and threads linked from there) for details.

Booster and brackets don't have to be from a '70, you can use the easier-to-find and more compact '73-'75 item, which also gives better, less mushy pedal feel. Find a used one and send it to Booster Dewey in Portland, OR for a good rebuild ("remanufactured" items are junk).

You'll need to make new master-to-prop-valve lines because the master cylinder will move upward and forward. Don't forget to put a couple of loops in each line, as the factory did, to allow flex without metal fatigue. Get a new name-brand (Bendix, Raybestos, United) master cylinder for 1974 Dart with power disc brakes.

And you'll need a suitable vacuum tap in your intake manifold.

 

[dustoff440]

Prop valve doesn't change, though you'll want to put smaller wheel cylinders in the 10" rear drum brakes to prevent the grossly premature rear lockup the disc brake A-bodies tend to have -- it's aggravated with power brakes. See here (and threads linked from there) for details.

Booster and brackets don't have to be from a '70, you can use the easier-to-find and more compact '73-'75 item, which also gives better, less mushy pedal feel. Find a used one and send it to Booster Dewey in Portland, OR for a good rebuild ("remanufactured" items are junk).

You'll need to make new master-to-prop-valve lines because the master cylinder will move upward and forward. Don't forget to put a couple of loops in each line, as the factory did, to allow flex without metal fatigue. Get a new name-brand (Bendix, Raybestos, United) master cylinder for 1974 Dart with power disc brakes.

And you'll need a suitable vacuum tap in your intake manifold.

Damn, this is more complicated and costly than I had originally thought. I think at this point he wife will have to lump it. LOL.

 

[slantsixdan]

If she finds the pedal too hard to push, you may be able to meet her needs by just swapping in a master cylinder with a smaller bore. This will increase the length of pedal travel and make the pedal effort lower. If you're presently running a 1-1/32" master cylinder, the pedal will be stiff, especially if you've got any kind of a semi-metallic brake pad composition. Regular organic pads, prepared before installation as described here and here will make the pedal less stiff, as will a 1" or 15/16"-bore master cylinder.

I still recommend the smaller-bore rear wheel cylinders, which will also help.