1948-1954 Power Brake - NonPower Brake Tidbit

As I play around with the early power brake systems in MOPAR's, I have found out a couple of interesting items to pass on.

Turns out that on the early power brake cars did in fact use a smaller pedal ratio. Although the pedals are identical between the power and non-power systems above the large pivot point. The are different below it.

The small leg on the non-power cars is 1.45 inches from the center of the pivot and the power cars it is 1.80 inches. Also the angle of the leg is further away from the M/C on the power brake cars. It also uses a special pushrod with an offset bolt eye. The standard pushrod will bind in the piston causing problems if used with the with the power pedal.

The other item is that this combination on the power brake cars causes the pedal stroke to be between 1/8 and 1/4 inch longer than the non-power setup.

At lease on the standard size cars all the power brake systems seem to use a 1-1/8 inch bore M/C. There is a chance that on the long wheel base cars that they used a 1" bore with power brake systems, but I have not been able to confirm that on an actual car. Conflicting info inthe books on that.

One other thing. On power brake cars they cut an 11" hole under the front seat in the floor pan and spot welded in a dome that looks like a salad bowl. This is so the booster unit will clear. This bowl extend up about 4 inches in the center.

In the event that someone out there wants to play around with early power brake systems, I hope that this information will be of use.

Best, James