blazerdup

I have an extremely hard brake pedal. It takes a tremoundous amount of pressure to get teh car to stop and then keep hard pressure on the brake pedal while at a stop light. I have all new brakes; shoes, lines, MC, wheel cylinders etc. The only thing I haven't changed is the proportioning valve since I upgraded from a single bowl MC to a dual bowl.

Is it possible that the proportioning valve is bad or what? There has to be a way to make it a bit easier to stop.

001mustang

Do you have front disc brakes?
Proportioning valve is used for front disc brakes.
Does your MC have residual pressure valves?
Does fluid flow freely out each WC/caliper when bleeding?
Are shoes and drums oil free and clean?
New or turned drums?

Tims65

What Master Cylinder did you install? If you have very little pedal travel and need to apply a lot of pressure to stop your car, your MC bore is probably too large.

Tim

blazerdup

I have drum brakes all the way around. Everything is new, drums and all. I bought the MC upgrade kit from CJ Pony Parts (DBC1), the one recommended on here in the FAQ as well. So.....is there another MC I should get? and how would I determine the bore size i need?

001mustang

7/8" to 1" mc bore is good for manual drum.

I doubt if your mc bore is bigger than 1".

Are your drums oil free.

Did you overheat and glaze your shoes by aggressive stopping or tight adjustment?

Is pedal high and hard? Just wanna make sure you bleed all air.

2+2GT

There is no proportioning valve on all-drum cars. A proportioning valve serves the split pressure requirements on disc/drum cars.

Was it this hard to stop before you converted the MC?

A smaller master cylinder bore will reduce pedal effort, and increase the amount of pedal travel.

I suggest you contact CJ and discuss the problem. If they cannot provide a MC with smaller bore, there's always the "Customer Review" box on the item…

http://www.cjponyparts.com/DUAL-BOWL...5-1966/p/DBC1/

blazerdup

No before swapping this stuff out it wasn't this hard to stop the car. I guess I am using the wrong term here, I have a distribution block that separates the brake lines. The brake lines go from the MC to the distribution block which then splits it off and the lines go to each wheel. Is this proportioning valve the same as teh distribution block that is standard on these cars?

2+2GT

The distribution block is a single, solid piece of brass with brake lines screwed to it.

A proportioning valve is a pressure regulator, that provides reduced output pressure in proportion to the input pressure, so your front disc brakes will function without locking the rear drum brakes, which require far lower line pressure.

Confusion arises several ways.

On Mustangs, from 65-69, the distribution block and proportioning valve were separate items, but from 1970-on, disc brake equipped cars had the two combined in a single assembly.

Beginning in 1967, all cars, even if equipped with only drum brakes, had a shuttle valve incorporated in the distribution block, to activate a warning lamp in the event of failure of part of the now-divided brake system. This is often mistakenly called a proportioning valve.

The 70-up disc brake counterpart incorporates all three, distribution, shuttle, and proportioning valve in a single assembly.

Confused yet?

F15Falcon

Bingo!!!

Jonk67

Did you follow the footnote?
"Please Note: The original push rod from your single bowl master cylinder must be reused to provide the correct pedal height and drive for the new master cylinder. Do not use the one included with the dual bowl master cylinder."

Just wondering since it also sounds like the pushrod may be too long and keeping the brakes engaged partially and you're just applying the last bit of pressure to fully extend them. Normally this occurs with the use of an adjustable pushrod that's extended too far.

Here are their installation notes, make sure you followed all of them:
Installation of a Dual Master Cylinder Conversion Kit:

1. The rear reservoir is for the front brakes. (This allows full pressure to the front brakes for proper brake balance.)

2. The front reservoir is for the rear brakes.

3. You must re-use the 64-66 pushrod on the new master cylinder. It is longer then the rod that comes with the 67 style dual master cylinder. If the 67 pushrod is used, a low brake pedal condition will exist.

4. The brass distribution block is used only for splitting the fluid to the left and right front brakes.

5. Remove the rear brake line from the brass distribution block.

6. The brass plug is for plugging the hole in the brass distribution block where the rear line was originally.

7. The first short line and union in the kit is to hook the rear line to the front reservoir.

8. The other short line in the kit goes from the rear reservoir to the brass distribution block.

Please note: Due to manufacturing variations on the 64-66 cars and the new master cylinder, adapter fittings may be needed for the lines and fittings. These adapters would be available at major auto parts stores such as NAPA.

Let us know what you figure out.
Jon