Packard Forum Index » V-8 (1955-56)

Working in very small spurts over the last few months, finally did my first test drive today after totally revising my earlier brake project. While that one worked, it was too ungainly, needed the carpet modified and levers turned out to be actually ugly in the engine compt.

Now for the current idea and a follow up question. For starters, can't say if this will work on anything other than a PB 56, brackets being one reason. Don't have anything else to look at but at the least shift linkage would probably need to change on regular 56's. While no Packards were damaged or actually mutilated, it also requires a bit of work so not a drop in. For that reason, won't go into much detail now as don't expect much interest. Can post a few in progress pictures if anyone is really curious.

Used the MPB 1" dual master cylinder, ABS dual 7 1/2" booster and revised the layout and linkage totally so it is direct acting. Uses a bellcrank but NO levers. Made a new pedal assy which is bent and slightly longer but supported with the same 56 brackets. I did add an extension which raises and moves the pedal out from dash another inch to provide full travel to the cylinder before pedal hits floor. All does look stock at first glance though. With the extra length and take off location to cylinder, the ratio is about 3.2 to 1.

Now the question. Darn thing almost threw me thru the windshield so is a bit more sensitive than I was expecting or would like. To change that, would you lower the ratio and chance there would not be enough oomph to stop if no power assist, would you do something different to reduce sensitivity or would you leave as is and learn to not have a heavy foot.

Howard,

Glad to hear about renewed progress on your MPB conversion and the revised pedal arrangement. But, some pictures would explain 1000 words worth.

As to whether the braking force is enough with no vacuum assist, the obvious answer (I'm sure you thought of it) is to test it that way.

As far as over-sensitivity is concerned, do you have front OEM drum brakes or discs converted? On my Patrician with a similar setup with disc brakes, the pedal is not overly sensitive with vacuum connected. Although not a direct comparison, earlier in my Pat's life, I do remember an overhauled BTV with OEM drums WAS very sensitive and I didn't like it.

Craig

I would prefer the sensitivity as u describe. Would also like to see pics.

Now that u have it running does this mean that u successfuly mounted the MC verticle as u had once indicated a few months ago????

Are u using a prop valve and/or a residual pressure valve???

Here are a few inprogress photos. Everything fits inside the vent opening and rod goes down behind insulator panel to booster. Did have to make a larger opening in the original toe plate so rod passes near steering column. Vent grill was turned upside down to take advantage of the large space. Made bellcrank pieces so it was open & air can still flow thru for my AC. Once everything final, will add some kind of bellows to keep air from engine cmpt getting into vent thru that space.

The master is at an angle but not straight up and down. Did the heat shield but think I will also add the ceramic insulator sheet to it and also add some insulation to protect the hoses. Not using a prop valve. Did leave the one residual valve to rear because it was used to join two sections of new line & would have had to come up with something else. MPB says they're not needed with remote fill masters where reservoir is high so didn't reinstall the front one.

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Ok. It took a while but i think i see how u did it. Slick set up. U deserve eng'eer of year award for it.

However on the RESIDUAL pressure valve:
Quote:
"Did leave the one residual valve to rear ... MPB says they're not needed with remote fill masters where reservoir is high so didn't reinstall the front one."

Better check some other sources about the function of the residual pressure valve. My understanding is that the Resisual pressure valve is for DRUM brakes only (especialy front). It keeps the shoe springs from retracting the shoes completely when foot is released from pedal. Has nothing to do with reservoirs.

AFIK all four wheel DRUM brake systems of any manufacturers used residual pressure valvels built into the master cylinder.

I'll keep an eye on it and not a problem to reinstall but as you say, the purpose is to prevent fluid from draining back if the master is lower than wheel cylinder. According to MPB as long as the reservoir is high, the gravity pressure of the fluid has the same effect.

According to Motors Manual 1963, Hydraulic Brake section p 165:
" The purpose of this (residual 8 to 12 pounds) pressure is to keep the wheel cylinder cups from leaking and to reduce possibility of air leaking into the system".

I suppose it's the slight pressure that keeps the wheel cylinder rubber cups tightly expanded against the bore of the wheel cylinder.

!963 Motors also indicates a DUAL master cylinder used on 62 Cad and Rambler. Has 2 residual pressue check valves.

Then shows a 'typical' master cylinder with valve. BAsed on my limited experience nearly all cars of GM, F and C production were hanging pedal and hi firewall mounted Master cylinders 1958 and later. Apparently all (or greatest percentage of production) had residual check valves AS WELL AS 4 wheel drum well into th e late 60's.

The earliest evidence i can find of disk brakes is 1968 as an OPTION. That is only checking among GM,F and C.

I think 1965 AMC products had power disc brake as an option/standard. My Rambler marlin supposedly had them standard. Early fifties Chrysler Imperial had discs as an option too. I wanna say Crosley had discs as well but not sure.