Our latest question comes from Rob. He asks: “I have a 1984 Chevrolet Monte Carlo and I want to convert it to manual brakes. Can I remove my power brake booster and use the same master cylinder to make it manual brakes?”
Excellent question Rob! At first the idea makes sense. If the power brake booster is what puts the “power” in power brakes, then removing it should be the only step, right? Not quite. The brake system is designed to work as a unit. Removing the brake booster would truly render the system “manual” but the effort required to stop the car would be MUCH higher than you’d expect. This all has to do with the size of the master cylinder bore and brake pedal ratio. My friend & fellow hot rodder Jefferson Bryant did an excellent write up on master cylinder sizing and pedal ratio that can be found right here. I highly suggest reading Jefferson’s article as it covers a lot of theory and includes some great technical information.
So the short answer is: no, you cannot convert a car to manual brakes by just removing the power booster. But lets dig a little deeper for a solution. The GM G-body vehicles (including Rob’s 1984 Monte Carlo) were built from 1978-1988 and included a LOT of vehicles:
- Buick Regal (1978–1987)
- Chevrolet El Camino (1978–1987)
- Chevrolet Malibu (1978–1983)
- Chevrolet Monte Carlo (1978–1988)
- GMC Caballero (1982–1987)
- Oldsmobile Cutlass Supreme (1978–1988)
- Oldsmobile Cutlass Cruiser (1982–1983)
- Oldsmobile Cutlass Salon (1986–1987)
- Pontiac Bonneville (1982–1986)
- Pontiac Grand Prix (1978–1987)
This broad spectrum of vehicles were all built on the standardized General Motors G-body platform, which means that a lot of the parts are mix-n-match. If you dig into the vehicle options from back then you will find that a few cars were available from the factory with manual brakes. The folks at the G-Body Forum have a great discussion thread about model years and parts differences for the factory manual brake cars right here. Even though we have not done this particular swap here at Ask My Car Guys world headquarters, it looks like you will need a manual brake master cylinder (with reservoir), a factory pushrod from the junkyard (or an adjustable unit), and an adapter plate for the firewall (since the brake booster is mounted with four bolts, and the master cylinder alone only uses two). You will also have to bend your brake lines a bit to attach them to the master cylinder (since it moves back a few inches). You brake pedal SHOULD have the correct hole in it already to mount the pushrod for proper manual brake pedal ratio (there is a great discussion thread with photos here on the G-Body Forum). That should be the bulk of the parts you need, from there it will be classic hot rodding “trial and error” to get everything working smoothly. It may be easy, it may not, you have to decide if it is worth the time and effort.
Another great resource is this discussion thread on the Hotrodders.com forum. This method uses some bits from a Chevrolet S-10 pickup and some good old hot rodding modifications to get the job done.
The bottom line is that when you want to change your vehicle from one configuration to another, start by looking to see if your vehicle was ever available with that option during its production life. This works for brakes, transmissions, engines, rear axles, even seats. There is no reason to re-engineer the vehicle when factory replacement parts may be available that bolt right in and are designed to work together.
Image courtesy of Wikipedia.