I'm putting all new brakes on my 72 Monte (long hood Chevelle).

It came from GM with Power disc/drum & frame mounted Combination valve.

Going to try Manual Disc/Drum & see how I like them. (cam makes low vacuum)

New parts:

Earls hyper-firm flex lines & SS lines from Inline Tube.

Master Power Brakes 1" master cylinder MC1702K (made for manual disc/drum + adjustable rod)

Fronts are 11" Summit disc & SSBC dual 38mm piston calipers.

Rears are Master Power Brakes big drum kit DR1700K, 11"x2" & 15/16" wheel cylinders (much cheaper & easier than adding rear disc brakes after cutting off ends of axle tubes for my Strange C-clip eliminator axle kit)

I think I will reuse my original Combination valve, as it looks fine & don't leak.

And now to my question, Do I need to add a 10# residual valve into my rear brake line??? (They are suppose to reduce pedal travel)

Thanks BBP

I thought if you had a drum master, they were already built in.

Bill,it should be built into the M/C. Call MP for confirmation.
Mike

My MC does have brass seats in the 2 ports, but I haven't tested for function.

Edit: I just tried to spray brake cleaner into them & neither lets it into mc bowls, so they act like valves.


Additional data:

http://www.hotrodheaven.com/tech/brakes/brakes4_index.htm

100# pedal pressure (6:1 ratio) with 1" MC = 764psi out of each port of MC

With 100# pedal pressure, my front caliper pressure (dual 38mm) 764# x 3.5158 in2 = 2,686#

my 5/16" rear wheel cylinder pressure (without typical 25% reduction from combination valve) = 527#

With typical 25% reduction from combination valve 527# x .75 = 395#

I don't know if these pressures are good or bad?

Larger front caliper pistons would clamp harder, but I don't know if my 1" MC would provide enough volume?

BBP

I called Master Power Brakes tech line, he didn't know much.

I did some air pressure testing on Master Cylinder & Combination valve.

Master cylinder is a 1" manual disc/drum. air passes freely in front port.

Rear MC port DOES have a residual valve in it, as I couldn't get low air pressure to make bubbles in brake fluid in the rear bowl.

The combination valve, front ports have no valving that I could find. Rear brake line port & MC rear port into combo. valve has a proportioning valve in there that stops air from both directions.

I don't think that I need to add a Residual valve into the rear brake line.

BBP