Modifications to a performance car take on a variety of forms, and for traditional muscle cars the most obvious mods are those underhood contributing to the "go." Probably just as important are changes just a little further down that focus on the "whoa." Safety is just as much a concern here as performance, especially considering many cars of the era were factory equipped with barely adequate drum brakes. Our '71 Plymouth Satellite project was thankfully equipped with the optional factory front disc brakes, a system greatly superior to drums, but even here we saw plenty of room for improvement.
The factory disc brake system on our Satellite is certainly a product of the industrial age, a time when iron was as cheap as the dirt it was processed from, and weight was far from a primary design concern. All of that metal, a single-piston pin-mounted caliper, and an overall rotor diameter of 11 inches, made for a cheap and effective braking system for its day, but it was a system that is admittedly primitive in contrast to what is generally seen today. We definitely recognized the opportunity for an upgrade, with a goal of installing a system that is both better and lighter, adding to the braking performance as well as to the overall gains achieved though reduced weight.
Wilwood offers exactly the system we wanted: a lightweight disc conversion using a fixed caliper system, and larger diameter 12.19-inch rotors for improved mechanical advantage. We looked at our entire braking system and made the decision to re-vamp the whole thing, using Wilwood's "Dynapro 6" 12.19-inch, six-piston kit up front, and the "Dynalite Pro-Series" 12.19-inch four-piston kit at the rear. At the same time we would heave the heavy iron master cylinder and power booster, going to a manual system, and add an adjustable proportioning valve to allow tuning the front/rear brake bias.
Since the Wilwood kit is designed to retrofit factory drum brakes, replacing the front disc brakes on our Satellite required a swap to the drum brake spindle. We found the front brake swap to be a simple upgrade, and the weight savings were substantial at nearly 40 pounds total. With the bigger brakes, wheel fit was a question with our aftermarket 15-inch wheels. According to a source at Wilwood, the 12.19-inch brake system will clear some 15-inch wheels, but interfere with others, depending upon specific wheel design. We found our 15-inch forged alloy Cragars by Weld Wheels cleared.
Discarding the factory iron master cylinder and brake booster and converting to the Wilwood aluminum master cylinder required an OEM manual brake pushrod and manual brake firewall reinforcement plate. The Wilwood master has a two-bolt pattern rather than the four-bolt pattern used by Mopar until 1979, so we drilled our plate, firewall, and pedal bracket to match. Since the two-bolt late Mopar aluminum master cylinder is a popular swap (same bolt pattern as Wilwood), a master cylinder adaptor is available from Mopar Performance and other Mopar vendors which will allow the Wilwood cylinder to bolt up without drilling. Another consideration is the need for a manual brake master cylinder pushrod, since the power brake pushrod arrangement will not match with a manual brake conversion. We found the Wilwood master's piston comes without the machining for pushrod retention, so it is imperative that a positive pedal stop is incorporated.
At this stage of the project, we installed the front conversion, master cylinder, and proportioning valve, while retaining the rear drum brakes. The rear disc conversion requires aftermarket "green" non-adjustable rear axle shaft bearings with snap-ring retention, and is not compatible with the factory tapered roller bearings. Since future plans call for a narrowed custom rear housing, it would be money down the drain to re-bearing our current axle shafts. The rear brake assembly will be included in the rear end build when we make the swap. Wilwood's proportioning valve allowed us to adjust the bias to accommodate the drums in the rear, and we can later dial in the braking system for the discs out back with a simple twist of the valve.
WHERE THE MONEY WENT PART NO.: DESCRIPTION: PRICE:* 140-10740-D Front kit, 12.19 rotor, drilled $1,167.95 260-8555B Master cylinder, 1-inch, black $239.95 220-7699 Flexline kit, universal, 16-inch. $59.95 290-2210 Brake fluid, (6) 12-ounce bottles $47.95 260-8419 Compact proportioning valve $41.95 Misc Brake line $9.95 Total: $1,567.70 *Prices as listed from {{{Summit}}} Racing Equipment