Whether a stock restoration, a weekend cruiser, or modified for maximum performance, the vehicle’s braking system is hands-down the most important system. When I brought my first Pontiac restoration project home many years ago, my dad said, “I don’t care how fast this car goes; it damn well better be able to stop.” With that, we rebuilt the braking system. It ran and stopped, but before the repairs were made, I almost crashed into my parents’ house, relying on emergency brakes when I was moving it in our driveway with rotted-out brake lines and frozen wheel cylinders.
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We laugh about it now, but it was one of the scariest experiences of my life the accelerator became stuck and I was hurtling toward the house at full throttle without any brakes. I did get it stopped without damage to anything other than some rather deep tracks in the front yard. A quarter of a century later, dad’s advice still holds true and my parents’ house escaped injury, no thanks to me!
In the case of Pontiac GTOs, especially the early ones, the braking systems were not nearly as high-performance as the engines were. The factory-supplied Delco-Moraine drum brakes were the norm back then, and fortunately, replacement parts are available from a variety of sources. By today’s standards, they are barely adequate at best and dangerous at worst, not exactly the epitome of a well-balanced performance machine. Even back then, road testers complained about the braking performance, and that there was not an optional braking system that was any different from what could be had in a six-cylinder Tempest sedan. The idea of hauling down a 3,500-pound car from triple digits while relying on a single master cylinder and four fade-prone 9.5-inch drum brakes is mind-boggling, yet that was all that was available for the 1964–1966 model years.
Sure, there were some upgrades available, such as semi-metallic linings and aluminum drums but they were more Band-Aid solutions and didn’t offer enough of an improvement to be considered problem solvers in anyone’s mind. That situation continued through the 1966 model year, even as optional horsepower levels continued to climb and GTOs became heavier.
It was not until the 1967 model year that the braking situation was improved in a significant way. That year, a dual-chamber master cylinder was added to prevent total brake loss if a brake line broke, and front disc brakes were made optional.
The new braking system was a huge improvement over the previous four-drum setup and featured four-piston calipers and 11.12-inch two-piece rotors. Disc-brake-equipped cars also received a larger 1.125-inch master cylinder bore size, compared to the smallish 1.000-inch size still used on drum-braked cars.
For the 1969 model year, the braking system was revised somewhat. To help correct leakage problems and the resulting warranty costs, Pontiac came out with a new, simpler, front disc-brake system, which was optional in the GTO and other A-Bodies. It featured a new single-piston caliper and a slightly smaller 10.9-inch vented rotor. The pistons were also less prone to cock ing and getting stuck in the bores. This system remained pretty much unchanged through the 1972 model year.
The A-Body was completely redesigned in 1973 with a heavier frame, a new Colonnade body style for increased rollover protection, and revised front and rear suspension systems. The brakes were upgraded as well, owing to increased safety concerns and a significantly heavier overall curb weight. While the 9.5- inch rear drums remained from the previous generation, the standard braking system now featured 11-inch front disc brakes; the front drums were finally put to bed. The extra weight of the new platform was obviously beyond any consideration for using them.
When the GTO option package was shifted over to the smaller and lighter X-Body Ventura platform, the braking system once again returned to four-wheel drums as standard equipment. They were 9.5-inch units and the optional front disc brakes were the 11-inch units used on the A-Bodies. All the listed systems were shared with various GM A-Body and X-Body offerings, as well as other platforms.
Repair or Replace?
It is reasonable and customary for much of the braking system to be replaced in the restoration process. While it may be possible to save certain items for the sake of originality, it is usually desirable to have fresh, new, and undamaged pieces going back on the car because the brake system is the most important safety system on the car and it shouldn’t be compromised. It makes sense to save the backing plates and perhaps rebuild the calipers and master cylinder if they aren’t too corroded, but beyond that, everything should be replaced with new items. If your budget can include correct calipers and a master cylinder, go for it. Most restoration parts houses have replacement brake parts in stock.
If you are restoring a car for a points-judged show competition, there are a couple of areas where you are probably going to be stuck with used parts where a better performing new part would otherwise be preferable. For example, the two-piece rotors used on 1967 and 1968 GTOs only recently began being reproduced. A single-piece replacement rotor was available that fits the application, but it is not factory correct. For a driver, this is a non-issue, but if you are going for the gold, you need the correct pieces to avoid having points deducted. In the past, it was necessary to re-use existing pieces or, if needed, find better examples. Though it appears that the problem has been rectified with this new release, I have not seen the reproductions, and therefore cannot verify that they are indeed correct enough looking to satisfy judging requirements.
Fortunately, the sheer number of GM A-Bodies still on the road today, and the large market that exists for these cars, the aftermarket offers a variety of parts that restore and even upgrade these vehicles for daily-driver or high-performance use. From brake lines to drums, rotors, pads, shoes, master cylinders, wheel cylinders, and even front and rear disc brake conversion kits, just about everything you need is available. These replacement parts also benefit from improved metallurgy, and while authentic looking, they also perform better and last longer than the original equipment.
One of the most complete catalogs of reproduction and aftermarket brake parts can be found at Inline Tube. Owner John Kryta has had an obsession with correct restoration products for many years. This has driven him to start and run a very well-respected business with top-quality parts. He began his business by offering perfect reproduction brake lines and he expanded from there. Year One, Ames Performance Engineering, Original Parts Group, and The Parts Place also do a very good job with brake parts but for the really hard-to-find items, Inline Tube is one-stop shopping.
Check for Condition
When it comes to evaluating your GTO’s braking system, start by focusing on some of the more common problems and typical repair and replacement required for overuse or simple age. Wear items, such as brake pads, shoes, rotors, and drums, should be replaced. New brake lines should also be part of the program, preferably in stainless steel to avoid further corrosion problems.
If the braking system is working properly, the wheels spin with very little resistance and do not make any noises that would indicate damage or frozen components. The actual contact surfaces the rotors and drums appear smooth, with very little in the way of imperfections. The surface may have a slightly wavy appearance, but there should be no discoloration, grooves, or gouges. Rust on the contact surface indicates improper seating of brake linings.
Additionally, there should be no wet spots on any of the brake lines and no seepage from the master cylinder or wheel cylinders. Any brake fluid puddles under the car need to be addressed before the car is driven.
The three main things to be looking for are leakage, uneven wear, and outright damage.
Following the path of the brake fluid from the master cylinder to the wheels likely shows some leakage of brake fluid. Obviously, this is not a good situation, as hydraulic pressure pushes the brake fluid out with great force. Eventually, there is not enough brake fluid to operate the brakes and the car no longer stops. Typical leakage spots are found around the fittings joining two assemblies, such as the master cylinder to the brake line and the brake hose to the wheel cylinder. The lines themselves can corrode and leak from pinholes, and lines weakened by corrosion sometimes break under the pressure. The early cars with a single master cylinder are especially vulnerable (they lose pressure and braking force to all four wheels sometimes), and cars equipped with a dual master cylinder do not suffer a full loss of brakes (either the front or rear pair still functions).
Repairing leaks is typically taken care of in a total brake system rebuild and/or replacement. New lines, master cylinder, and wheel cylinders replace defective items as long as they are properly installed.
When inspecting your brakes, look for uniformity of wear. Though your rotors may look fine, it is possible that the brake pad on one side of the rotor may have worn more than on the other side. This is actually a pretty common situation and can be felt by the car pulling to one side or the other.
The problem is usually caused by one of the pistons being frozen in the bore and not applying pressure to the rotor, though other rusted/broken/stuck hardware can cause similar problems. The car still stops, but braking force is significantly reduced.
Drums and rotors are exposed to extremes of heat, cold, torsional stress, and pressure, but they are designed to handle those conditions, within common operational constraints. When typical operating conditions are exceeded, specific types of damage can occur. Excessive heat from repeated high-speed bursts, towing, and racing can manifest itself in the way of bluing of the metal and cracks. Additionally, galling of contact surfaces is also a common consequence when the linings become damaged by the intense heat.
In all cases, regardless of the type of restoration, these damaged items should be replaced whether or not correct replacements can be found. If you have this level of damage and are restoring a car for points-judged competition, find used parts in better condition or use possibly incorrect reproduction items until you can find more correct examples. Any rotor or drum that is gouged, blued, cracked, or similarly damaged needs to not only be replaced but properly disposed of so it is not re-used at some point in the future.
With the current popularity of pro touring, many owners want their older cars to perform on par with or better than a new high-performance vehicle. Even if you are not looking to build your GTO into a competitive road racer, chances are that you want your car to be able to stop at least as well as a modern passenger car.
Fortunately, the aftermarket has come to the rescue with a variety of options. Kits are available from most restoration outlets that bring your drum-braked GTO up to 1973-and-up specs, and you can even upfit those items from your auto parts store, though the kit approach is more attractive from the parts and completeness standpoints. If you are more adventurous, other kits are available from places like Baer Racing, Stainless Steel Brakes, and Wilwood Engineering that can outfit your car with options from high-performance street to a truly race-ready system. The only limitations are your preferences and budget; there is an amazing amount of brake options for these cars in the aftermarket. Keep in mind that depending on the system you choose, you may not be able to use OEM wheels.
Master Cylinders, Proportioning Valves and Lines
As part of a brake system upgrade, you are left to sort out the many options in the areas of master cylinders, proportioning valves, and brake lines. Every case is likely to have unique requirements. Depending on the year of your particular GTO and the configuration of the front brakes, you may be able to work with what you have or you may have to upgrade. Either way, it is imperative that the front and rear brakes work efficiently and in harmony with each other, and it’s your job to make sure that happens.
For safety’s sake, make sure your brake lines are in good condition. Replace whatever is needed to ensure they are all up to snuff. A modern master cylinder should be used. If your car came from the factory with a disc/drum setup, you can reuse the stock unit, provided that the egg-shaped pressure booster in the rear lines is removed. Its job is to increase the line pressure to the drums, as they require more pressure to use than the discs. It is not required with rear discs.
Next, installing an adjustable proportioning valve helps tune the proper front-to-rear balance. You don’t need to remove the proportioning valve at the master cylinder, though an adjustable proportioning valve must be downstream of the distribution block. A Wilwood unit costs between $40 and $80, depending on whether you want a lever (PN 260-8420) or more economical knob style (PN 260-8419). A popular mounting point is on the frame, near the front of the side rail.
If you have a four-wheel-drum system, are upgrading to discs up front, and want to go the aftermarket route, Stainless Steel Brakes, Wilwood, Baer Racing, and countless others market affordable, high-quality master cylinders that generally run around $200.
1964 Rear Drum Brakes
The 1964 10-bolt rear ends have additional issues to overcome. Since there is no separate retainer plate to hold the bearings in the rear, you must take the old drum brake backing plate and cut out the material that mounted up against the axle. This material can then be used as a shim behind the new backing plate. Slide all the parts over the axle in reverse order of final assembly and press on the bearing. Other than this particular bit of cutting, everything else is the same.
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