Heads up to those that install a 2 bolt aluminum master cylinder.
With the prices of these being about the same as a new or rebuilt cast iron 4 bolt MC, the aluminum units are a great option. I've found a small glitch though.
In 2012, I wanted to convert my power brake '70 Charger to a manual MC setup to shed weight and to reduce clutter. I had problems with getting adequate stopping force after trying 4 different MCs. I gave up and put the power booster back on.
In June, I pulled the engine for a rebuild and decided to try again with a few changes to ensure that it would work right.
It did not. Once again, I was disappointed. Braking at low speeds was fine but above 20 mph, it wasn't. With some unresolved angst, I put the power booster back on but was still curious about why I couldn't make the manual setup work right. I have driven several manual disc-drum A body cars and was always impressed with the braking. These always had the stock iron 4 bolt master cylinders though.
In the Charger I have the Dr Diff 13" front brakes and the 11.7" rear kit so the car should stop.
I felt that something was wrong and I may have stumbled upon it.
Today I got the manual MC out and the booster in. As I was bench bleeding the 1 1/8" MC, I noticed that the front port got the fluid first and the bubbles first. The rear port only started pushing fluid about 1/3 the way into the stroke. Usually, the front port serves the rear brakes while the rear port serves the front.
With the brake lines connected the traditional way, the REAR is getting pressure before the front.
This can't be right.
I tested a stock iron 15/16' MC and front and rear get pressure at the same time.
I tested the Dr Diff aluminum 15/16" MC and it was exactly like the larger 1 1/8" version: Pressure and bubbles at the front port before the rear.
There was no tech sheet in the box with these master cylinders but Mancini Racing includes this sheet:
The ports are REVERSED.
Is this common knowledge? I am no expert but I'm a decent mechanic on these cars. Reversed ports aren't completely unusual. I had a '78 Trail Duster that had a MC with reversed ports like this.
Just a warning to those that may run into the same problem.
With the prices of these being about the same as a new or rebuilt cast iron 4 bolt MC, the aluminum units are a great option. I've found a small glitch though.
In 2012, I wanted to convert my power brake '70 Charger to a manual MC setup to shed weight and to reduce clutter. I had problems with getting adequate stopping force after trying 4 different MCs. I gave up and put the power booster back on.
In June, I pulled the engine for a rebuild and decided to try again with a few changes to ensure that it would work right.
It did not. Once again, I was disappointed. Braking at low speeds was fine but above 20 mph, it wasn't. With some unresolved angst, I put the power booster back on but was still curious about why I couldn't make the manual setup work right. I have driven several manual disc-drum A body cars and was always impressed with the braking. These always had the stock iron 4 bolt master cylinders though.
In the Charger I have the Dr Diff 13" front brakes and the 11.7" rear kit so the car should stop.
I felt that something was wrong and I may have stumbled upon it.
Today I got the manual MC out and the booster in. As I was bench bleeding the 1 1/8" MC, I noticed that the front port got the fluid first and the bubbles first. The rear port only started pushing fluid about 1/3 the way into the stroke. Usually, the front port serves the rear brakes while the rear port serves the front.
With the brake lines connected the traditional way, the REAR is getting pressure before the front.
This can't be right.
I tested a stock iron 15/16' MC and front and rear get pressure at the same time.
I tested the Dr Diff aluminum 15/16" MC and it was exactly like the larger 1 1/8" version: Pressure and bubbles at the front port before the rear.
There was no tech sheet in the box with these master cylinders but Mancini Racing includes this sheet:
The ports are REVERSED.
Is this common knowledge? I am no expert but I'm a decent mechanic on these cars. Reversed ports aren't completely unusual. I had a '78 Trail Duster that had a MC with reversed ports like this.
Just a warning to those that may run into the same problem.
