Jump behind the wheel of nearly any late-model car, and you will soon realize the benefits of it relying on a power-assisted braking system of some sort. Sometimes the system is vacuum boosted, and sometimes it is hydraulically assisted, but regardless of which type is used, the benefits of having a power-assisted brake system are readily apparent.
If you’re like Phil Sanner of Lakeland, Florida, and jump out of your late-model daily and into your classic, you quickly realize the classic could probably use a brake upgrade that includes some variation of power assistance. After a quick search on the interwebs, he found just what the doctor ordered at Tuff Stuff Performance.
Cars like Phil’s Nova — those with manual brakes — rely on brake-applying pressure that is directly related to the amount of force coming from the driver pushing down the brake pedal. The harder you push, the harder the brakes clamp. However, the switch to power brakes adds — in this case — a vacuum canister with a diaphragm that assists with the applied pressure. This means less effort is required from the driver.
Phil’s ’71 Nova did not come from the factory with disc brakes, however, someone added them before he acquired the car. Whether your car has a disc/drum or drum/drum system, an upgrade like this vacuum-assisted power brakes does not require a complete system change, you can add power assistance to both styles. I do want to make one thing clear, do not expect your brakes to work exponentially better just by adding a power-assist unit. The power-assist unit simply aids with pedal pressure applied to the master cylinder. It will not apply any more braking pressure than the calipers or brake shoes can create.
In some cases, you may be required to add a vacuum pump to reach the required 18 inches of vacuum. – Matt Oliver
All About The Pressure
This install features an “aid” which is achieved via a vacuum hose that is connected from the booster (vacuum canister mounted behind the master cylinder) to a vacuum port on the engine’s intake manifold. As the engine vacuum is introduced to the booster, the vacuum pulls one or more diaphragms that act on the master cylinder when the brake pedal is pushed. The larger the diaphragm’s area, the more pressure the booster can provide.
We’ll use Phil’s car as an example: The Nova has a dual-reservoir master cylinder with a 1-inch bore and no vacuum assist. With the 7:1 pedal ratio and the application of 100 pounds of force on the brake pedal, he is creating 891 psi of brake pressure. When we add the Tuff Stuff recommended power brake unit, he will increase that pressure to approximately 2,000 psi. That means he will not be required to push the pedal as hard to achieve the same braking response.
Size Definitely Matters
For the upgrade to Phil’s Nova, Tuff Stuff Tech Manager, Matt Oliver, recommended PN: 2127NB-1 combo package. This upgrade consists of Tuff Stuff’s 11-inch single-diaphragm booster and dual-reservoir master cylinder with a 1-inch bore. When contemplating a brake upgrade, it’s important to remember that all master cylinders are not created equal. Other than the obvious single-pot and dual-reservoir configurations, the piston/bore diameter within the master cylinder is an important aspect that must be considered.
The piston-bore size within the master cylinder directly affects how the brake system feels when you push on the pedal. The most common sizes are 3/4-inch, 7/8-inch, 1-inch and 1-1/8-inch. In some cases, you will find the bore size of a given master cylinder stamped somewhere on the body of the master cylinder. Which bore size is best for your application depends on the other components of your brake system. Whether you have manual or power-assisted brakes, as well as caliper volume, will all need to be factored into what bore will actually work best for your application. When planning an upgrade such as this, it is best to first consult with the manufacturer of the brake system you will be using so you can be sure to get the right master cylinder for your application.
If you are ready to install vacuum-actuated power brakes on your car, having an engine that creates enough vacuum is of utmost importance. Many hot rodders have built their engines with larger-than-stock camshafts as well as other horsepower enhancements. This is great for engine performance, but could have a detrimental effect on vacuum-assisted power brakes. It’s no secret that engine vacuum decreases as camshaft duration is increased. I have seen many cars that idle with less than 8 inches of vacuum. This is simply not enough for proper actuation of the brake booster. In fact, the folks at Tuff Stuff Performance actually recommend a minimum amount of vacuum for proper operation.
“Our boosters require a minimum vacuum of 18 inches,” says Matt. “If you do not have enough vacuum, you will have weaker power assist. This will in turn affect the safe stopping power and distance for the vehicle. Our Tuff Stuff boosters are built, inspected and quality tested at 23 inches of vacuum to assure the optimum 18-inches of vacuum can be utilized.”
Before You Start
If you decide to tackle an upgrade like this, plan on a couple of evenings after work or a solid Saturday to complete the job. It is a task that can be handled in the home garage with simple hand tools. However, before you lay down your hard-earned cash, Matt has a few suggestions.
“A good tip for enthusiasts to consider before they order anything would be to know what the vehicle requires for a direct fit before trying to modify a universal set up to the application,” Matt states. “In some cases, you may be required to add a vacuum pump to reach the required 18 inches of vacuum. Also, when switching from a manual to power braking system you might also need to change out the brake pedal from a manual brake pedal to a power brake pedal. It is imperative that you have the correct pedal ratio and angle from the pedal assembly into the booster and master cylinder.”
Since Matt mentioned different brake pedals, let’s explain what he’s talking about. Most GM brake pedals have two holes in the pedal’s arm to be used for connecting the master cylinder pushrod. Using the correct attachment hole gives the correct pedal ratio depending on whether you have manual or power-assisted brakes. The hole closest to the pedal’s pivot is for use with manual brakes and the one below it is for those utilizing power-assisted brakes.
With a manual disc/drum arrangement, using the upper hole gives a pedal ratio of 6.2:1. Since a power-brake booster increases the force applied by the pedal, a lower pedal ratio can be used. Most vacuum-boosted vehicles can use a pedal ratio of 3.2:1 to 4:1. Phil’s Nova has two holes in the “arm” to deliver different pedal ratios. This means the current pedal is able to be used for either a manual or power-assisted system.
One of the things we did that you might not have to worry about, is replumbing and relocation of the proportioning valve. Whoever installed the disc brakes never mounted the prop valve to anything, it was being supported solely by the brake lines. It looked like a mess of unsafe and twisted lines, and the mess needed to be addressed. We found a prop valve mounting bracket online and added it to our install. The hardest part of this install was bending and flaring the brake lines because of prop valve relocation.
Whether your car has disc or drum brakes, adding a Tuff Stuff vacuum-assisted brake control is a surefire way to improve how enjoyable your car is to drive. Let’s face it, if the upgrade exerts more force on the brakes while you apply less pressure to the pedal, the less force exerted by you is sure to make things more pleasurable when racking up those miles.