Building my brake system

1970 Cuda, 10-in rear drums, 11-in front rotors from a 1973 Dart. Manual disc/drum, and the Dart was also manual disc/drum.

My first question is about the prop valve ass'y, I got the valve ass'y from the Dart. It is (looks like) PV6070MOP.
In the Dart, apparently there was no metering "hold-off" valve. Please see pics. It seems to me the Dart had essentially
the same braking system I will be using, so why would one car need the metering valve ?

Second question is compatibility of the hydraulic parts. I need to buy a master cylinder, both front calipers, and both rear wheel cylinders.
Researching this, I'm leaning towards a 15/16 MC, 2.60-piston front calipers, 7/8-in rear cylinders.
I have 28" rear tires and 26" front tires.
Weight distribution: Car is a BB 4-speed 70 Cuda with power steering and battery back in the truck. 26" radiator, no A/C.

I'll probably go through Dr Diff for everything, including advice, but thought I would post here too.
Your advice and critique are much appreciated !

Disc brake A bodies had a tendency to lock up the rears. Hold off allows both the front and rear brakes to apply simultaneously.

Might not want to emulate that system.

On my 70 cuda, I have a 15/16 master, 2.6" front calipers on 11" rotors, 7/8" rear wheel cylinders with 11x2.5 drums. I am just about to start driving it in the next two weeks after a long overhaul, so I can provide feedback soon. The pedal feels pretty good just from bleeding and stationary pushes.

I was concerned that using a 15/16 master plus 2.75" calipers would produce too long of a pedal travel - based on my research it's a mixed bag, some people say it's fine, others have had issues. Rear drum adjustment plays a big part of the pedal travel. On paper, the 15/16 master + 2.6" calipers was a better combination than the 1.032 master + 2.75" calipers using the same input force.

For the valve, I kept the drum/drum distribution block and added an adjustable wilwood proportioning valve going to the rear brakes.

Hurst Guy, Thanks a bunch, that would be fantastic. Good Luck

As a quick update, it seems to be fine from around town driving. Taking it to the track in a week, so we'll see how it does there. I'm having issues keeping the car running under hard stops, so the brakes are outperforming the car at the moment. We just put a 1" MC on my friends challenger with 2.75" front calipers/11" rotors and the smaller rear drums, we'll try that this weekend around town - pedal feels really good from in-garage testing, we'll see how it is on the street.

Try adjusting the float level down a tiny bit on the stock type Carter carbs or add slosh tubes if it has a Holley carb

Thanks - it's a six pack set up - float levels were too low and idle screws need to be turned out slightly in the outboards. We were deceived on float level settings because we had a mechanical pump putting out too much pressure that was pushing past the needle/seat.

I've still been happy with my manual brake setup - have some rear drum issues (too much to explain) but I'm re-doing those next week and should have some final testing towards end of month.

I am curious, what size brake lines are you running with your manual brake set up? My buddy has a Demon 340 with aftermarket front disk and rear 10.5 inch factory drum brakes. You really have to stand on the pedal to get it to stop in a foot ball field distance.
I do not know what size master cylinder or calipers or wheel cylinders he has on it. I do know from just looking at it, it is a later model Dakota type MC.
Thanks Jerry

if you have to stand on it that hard he has the wrong diameter master cylinder on there. the later model aluminum masters had larger bores to use with power brakes. ideally he needs to find a 15/16 inch bore master cylinder to use with manual brakes.

15/16" master

https://www.amazon.com/gp/product/B001PYO1PU/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I would strongly advise to ANYONE that might be contemplating a HYDROBOOST system to buy a complete kit with a 100% money back warranty if it does not work.
I was given a new hydroboost unit with no hoses, no instructions and struggled for a month with it.
The deal was, I would get it for free but had to figure out everything and report back about it. I bought a new 1 1/8" master cylinder, I shaped and formed the hoses and fittings, the hard lines and sourced the special power steering reservoir that had 2 return line nipples. I could not get any boost out of the unit. The damn thing also led to the failure of 2 good power steering pumps. I suspect a bad HB unit. I intend to pull the stuff out and try a manual 15/16" master cylinder.

You lost me…is somebody talking about a hydro boost system in this thread?

don't forget, a manual brake setup uses a different pedal ratio than a power setup, with 6 or 7 to one being about ideal.
then as said, a small[er] master cylinder bore, and larger [meaning more piston area] caliper size.
however, with that said, it's a balancing act. all of the above need to work as a unit to get the best results.
reading the "brake" sticky by member feets is well worthwhile, and can shed some light on things one may not have thought of.

I didn't ask for you to comment, yet here you are. Try this: DON'T follow me around to comment on my posts, it makes you look like a lovestruck teenage girl.

I wrote this in open terms just as an advisory notice to anyone that looks to build some brake system on the fly and deviate from the factory stuff. Sometimes doing custom stuff works out well. Sometimes it doesn't.

Oh my my, sensitive today aren’t we? LMAO.