I want to change the brakes on my 1972 charger, from drum to disc. Any suggestions?
Tuesday, August 2nd, 2011 AT 5:40 AM
Make sure you have a donor car nearby. You'll need the correct combination valve that sits on the frame rail right under the master cylinder. It is calibrated for the vehicle's weight distribution to reduce rear wheel lockup. Replace the master cylinder. The old one has residual check valves for both the front and rear hydraulic circuits to maintain 10 psi on the system. You don't want that pressure with disc brakes.
Tuesday, August 2nd, 2011 AT 6:08 AM
But im getting my engine beefed up and my current brakes wont be able to withstand the power.
Tuesday, August 2nd, 2011 AT 6:17 AM
Increased horsepower makes the car go faster, it has nothing to do with stopping. Brake systems are designed for the weight of the car. The system has no idea how powerful the engine is.
I forgot to mention that you have to look at the rear brakes too. Their stopping power was matched at the factory to the strength of the front brakes. You need to look at the drum inside diameter, the shoe width, and the wheel cylinder inside diameter. For the first two you use a tape measure. For the wheel cylinder, the messy way is to pull out one dust boot, piston, and lip seal, then look at the diameter molded in the inside surface. You can also check places like rockauto. Com to see what they have listed for your car with and without front disc brakes. If you're real lucky, the rear brakes will be the same for either application. That will make the swap much less complicated.
You also have to consider the power brake booster. Drum brakes are self-energizing meaning they tend to apply harder due to the rotation of the drum. Disc brakes don't have that characteristic so a lot more fluid pressure is needed to produce the same stopping power. That's where the power booster comes in. I only added a booster to one car many years ago and it was a real pain, but that was on a '72 Mercury. That one ended up needing two more holes drilled in the firewall to mount the booster, then the push rod was different so we had to change the brake pedal. Chrysler used to be noted for lots of parts interchangeability so chances are you're not going to have as many issues.
The biggest variable in the braking systems has to do with the weight of the engine. If your car came with a small block, (318, 340, or 360), and that's what's going in it now, the weight will be staying the same. Same with a big block. If it came with a 400 or 440 and you're putting in another big block, you're fine. It's when you go from a six cylinder to a V-8 or from a small block to a big block that the weight distribution changes. Of much more importance than the brakes is the front torsion bars. Simply adjusting them up is not the solution. You'll want the torsion bars designed for that body with that engine. Again, if you're staying with your original engine, none of this weight distribution discussion applies.