One area hot rodders, racers and custom car (and truck) builders tend to ignore is the brake master cylinder and, in particular, the actual brake pedal ratio. After all, it doesn’t make the car one bit quicker or faster, and if the thing stops,in the end, why worry? Pedal Ratio
The critical component in the braking equation is the pedal ratio. In operation, the brake pedal acts as a lever to increase the force the driver applies to the master cylinder. In turn, the master cylinder forces fluid to the disc brake caliper pistons or drum brake wheel cylinders. If you examine a brake pedal, you'll see the pivot point (where the pedal swivels) and the mounting point for the master cylinder pushrod are usually different. By varying the length of the pedal, and/or the distance between the pushrod mount and the pivot, you can change how much force (from your leg) is required to energize the master cylinder. This is the "mechanical advantage" or pedal ratio. This formula will help you figure it out: Input Force x Pedal Ratio ÷ Brake Piston Area = PSI.
Mathematical babble? The arithmetic simply equates to the amount of force exerted by your leg times the pedal ratio divided by the area of the brake piston(s). FYI, the typical adult male can exert roughly 300 pounds of force (maximum) with one leg—and that’s a bunch. Something in the order of 1/3 or 1/2 that figure is obviously more comfortable, even in a hardcore racecar.The average manual (non-power boosted) master cylinder requires somewhere between 600-1,000 PSI to be totally effective. Somehow, 100-150 pounds of leg force has to be translated into 600-1,200 PSI. The way it's accomplished is by way of pedal ratio. While changing the overall length of the pedal is possible, it's often easier and far more practical to shorten the distance between the pivot point and the master cylinder pushrod mount location. That's precisely how many racecar chassis shops modify brake pedals.
This manual master cylinder is one of the most common you’ll find in modified applications). It is based upon a Mopar configuration, and is sold by Mark Williams Enterprises and others. These master cylinders are available in at least two different bore sizes: 1.00-inch and 1-1/8-inch (a 1-1/32-inch bore cylinder is also available from some sources. This is very close to a 1.00-inch assembly, and it's sometimes called that). They’re manufactured with an aluminum body along with a relatively large capacity plastic reservoir with dual outlet bores (which correctly face the driver side fender when mounted in the car). 
The Mopar master cylinder has one shortcoming: The size of the outlet fittings. The front fitting is a 9/16-20-inch Inverted Flare while the rear is a 1/2-20-inch Inverted Flare. They’re not common. Lamb Components offers a solution. Lamb manufactures special adapters specifically for these master cylinders that allow an easy hook up to #3 A-N fittings. 
Look carefully at this piece: It’s a pushrod retainer engineered into the M-W master cylinder. The purpose? It positively retains the brake pedal pushrod. That means the pushrod can’t fall out if the pedal goes over center. And don’t laugh. It happens more regularly than you might think with modified cars.
The typical Detroit pedal assembly looks like this. This vintage Nova hanging arrangement is designed to accept the brake pedal assembly, and if equipped with a clutch, that too.
If you take close look at this pedal, you can see two different master cylinder pushrod mount holes—one is for a booster-equipped application, while the other is for a non-boosted brake arrangement. For a late model, non-boosted manual application, many fabrication shops modify the pedal assembly by creating a mount that is higher (up the pedal) than the original. By moving the mount position higher, the pedal ratio is improved.
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