If you search the internet, there are dozens of front disc-brake conversion kits for the 1964-’66 Chevelle, including a dizzying number of options for rotor diameters, multi-piston calipers, drilled and slotted rotors, and a small mountain of brake pads. The options alone would require Mr. Spock to use his fingers and toes.
Rather than become bogged down in all that detail, we decided to keep it simple. Don’t get us wrong, all those pre-engineered kits are great, and they offer all the parts. But to us, that’s like having UberEats deliver a sandwich. Sure, it’s the ultimate in convenience – but you are paying somebody else to do the work.
In situations like this, enthusiasts can do the work themselves and eliminate the middleman. Our approach to this disc-brake swap will be split into two sections. The first will outline all the parts you need (along with a few options) if all you want to do is replace the stock drums with factory discs. The second approach will detail what you need to do to add taller F-car spindles, along with the discs, to improve the handling geometry along with the brake swap. Both of these options can be achieved with parts sourced from Rock Auto and Summit Racing Equipment.
The first conversion is as simple as it gets for the bare-essential hot rodder who only wishes to drop the drums. Disc brakes did not appear in the A-body GM lineup until 1967, which was an odd four-piston caliper deal that is only important to the resto purists. By 1969, front discs had improved, and the single-piston floating-caliper design would become a near-universal GM brake arrangement. This is the simplest of the front disc conversions and even with its 11-inch rotor, this is still plenty of brakes to stop a street Chevelle even over repeated attempts.
We’ll show you how to easily convert an early Chevelle front drum-brake car over to discs with minimal cost. This will be the bare-bones basic version using mostly factory or OE replacement parts. The stock ’64-’66 Chevelle spindles can be machined to accept an aftermarket ’69-’72 disc brake caliper bracket, but finding a shop to perform this minor machining might be difficult if you live in a rural area. Here is where it would be acceptable to purchase new spindles and perhaps add a drop spindle to lower the right height at the same time.
This ’69-’72 package will bolt directly onto the front suspension on a ’64-’67 drum brake Chevelle. Everything else in this conversion is either a reproduction part (the caliper mount) or stock replacement pieces like the calipers, rotors, pads, and brake lines.
The only issue is, the stock drum-brake spindle’s upper caliper mount boss is too tall and must be machined roughly 0.250-inch to properly position the caliper mount. The mounting hole will also have to be threaded deeper using a bottoming tap. The cost of out-sourcing this machine work may justify purchasing either stock ride height or dropped spindles. We’ve included a couple of part numbers in the parts list for both versions.
As we mentioned, there are multiple companies offering this replacement disc brake package, and there’s nothing wrong with merely ordering one part number and bolting everything together. But if you do your research and price checking, it’s possible to piece this system together for less than the average complete package sells, and you will get the exact parts you desire as opposed to being stuck with a kit that may not offer the desired pieces.
A 1-inch taller spindle that can bolt on to early Chevelles come from two different junkyard sources. Unfortunately, both of these car models are now old enough that they are not as easily found in boneyards. But they can still be sourced from enthusiasts or aftermarket sources.
The B-car spindles came in 11- and 12-inch rotor sizes on ’77- ‘90 cars like the Chevy Caprice and equivalent Buicks, Oldsmobiles, and Pontiacs. When sourcing this spindle, be aware that the ’77 cars used a smaller spindle shaft for the outer wheel bearing and won’t allow the use of a larger 12-inch 1LE rotor (more on that in a minute). Also important to remember is to use calipers intended for that spindle application. So, if using a 1988 Chevy Caprice, the same application calipers must be used.
When using the larger, 12-inch spindles, police and other heavy-duty applications used a 5×5 bolt pattern, which is incompatible with the Chevelle 5×4 3/4-inch pattern. The remedy for this is the Gen III 1989 Camaro 1LE 12-inch rotors that retain the 5 x 4 3/4-inch bolt pattern. But – there’s always a qualifier in these stories – you end up with metric front lug studs. Yes, the lugs can be converted to SAE size but this requires a very specific press-in stud.
Early Chevelles can also use the 1970-’81 Camaro and Firebird spindles with matching rotors. Right off, this swap will require a custom ball joint that’s available through Global West that has the correct taper for the lower spindle that has been modified to press into the stock lower control arm. These taller spindles also come with an integral steering arm like the B-body spindles.
These spindles will use the stock Camaro 11-inch rotor and single-piston floating-caliper assembly. There are also aftermarket dropped spindles for these cars that could be employed if you want to drop the nose on your Chevelle at the same time. This swap would obviously use all the stock wheel bearings, seals, caliper rebuild parts, and pads for the ’70-’81 F-cars.
One supposed disadvantage to using the B- or F-car spindles is the steering arms are positioned in a slightly different place, which will cause bump-steer issues. Without getting too deep into this subject, bump steer is the amount of toe-change induced when the suspension moves away from at-rest ride height. This author has measured bumpsteer on cars equipped with both the stock Chevelle and F-car spindles and, frankly, the numbers are not good. However, the numbers only get really bad when the suspension moves beyond one-inch of travel on either side of ride height.
More importantly, these toe changes are almost entirely accommodated by deflection in the front tire sidewall The bottom line is, for street-driven cars, this induced bumpsteer is not an issue, despite what the “experts” in forums and even published books have claimed. We won’t go further into this because it diverts attention away from the focus of this story on brakes, but the issue is worthy enough to bring it up. The author’s ’65 Chevelle has been equipped with F-car spindles for over 25 years and has been autocrossed and road raced with no problem. Is it ideal? No. Does it work? Yes.
Another important consideration when changing to the taller spindles is that the integrated steering arms require different tie rod ends. The ’78-’81 G-body (Monte Carlo) or ’83-’94 S-10 truck outer tie-rod ends are an excellent substitute. Thankfully, the sleeve adjuster size is the same, so the new tie rod ends will bolt right in place.
Another issue with using the taller B- or F-body spindles is the taller height affects the stock alignment because now the stock upper arm is too long. This requires adding a large number of shims to relocate the upper control arm to properly position the camber and caster. For cars equipped with a big-block and headers, this presents a serious problem since the spacers will put the upper control arm right into the header tubes.
The solution is to use an aftermarket tubular upper control arm that is designed to work with the taller spindle. These arms from Global West, Detroit Speed, Heidts, Hotchkis, QA1, Summit, and a ton of other sources shorten the upper control arm while adding positive caster. These tubular upper arms also allow deeper-offset wheels in the front, allowing for wider and larger 17- or 18-inch tires if that’s part of your game plan. These tubular arms will certainly increase the cost of the brake conversion, so that also needs to be a consideration.
We should also mention that converting a drum brake car to front discs will also require a new, dual-reservoir master cylinder. For this story, we’re not going to get into all the variables with power brakes so we’ll deal with the simple application of using a non-power-assist master cylinder and a brake proportioning valve to balance the pressure front-to-rear.
Master cylinder bore diameter plays a big part in generating pressure. Physics dictates that a smaller master cylinder bore diameter will generate more pressure than a larger-bore diameter. Our experience with disc brake conversions like this has revealed that a master cylinder with a bore diameter of 7/8-inch will generate acceptable line pressure to the calipers without undue force on the brake pedal. This will still require more pedal effort than your wife’s Honda or a 2020 Camaro, but will still be acceptable for a ‘60s muscle car.
We’ve found that a 1978-’80 Monza master cylinder utilizes a 7/8-inch piston-bore diameter, will bolt up to a typical Chevelle firewall, and work with the brake pedal actuating rod. We’ve included the master cylinder part number with the accompanying parts list. Cars with a power brake booster can run a 1-inch master cylinder and will probably work fine.
Parts List A (’69- ’72 Drum-to-Disc Conversion)
|Stock height spindles||SUM-CK-101-1||Summit Racing|
|2-inch drop spindles||16472||Summit Racing|
|Leeds caliper mount||LED-SPBR5001||Summit Racing|
|Caliper (left)||AAZ-18-4040||Summit Racing|
|Caliper (right)||AAZ-18-4039||Summit Racing|
|Master cylinder (7/8-inch bore)||MC39027||Rock Auto|
|Wheel bearings (outer)||NBA2||Rock Auto|
|Wheel bearings (inner)||NBA6||Rock Auto|
|Brake hose||BH36616||Rock Auto|
|Brake fluid||10-4110||Rock Auto|
|Spindle nut and washer||04993||Rock Auto|
Some people have taken issue with the smaller 7/8-inch master cylinder, thinking that the pedal does not feel right. The issue is not that the pedal feels spongy – although that is the most common description of the problem. The issue is, the smaller piston diameter requires more pedal travel to move sufficient fluid from the smaller piston to create pressure. This means the brake pedal will move slightly farther than with a master cylinder with a larger piston diameter of 1-inch, for example. This causes some enthusiasts to complain about this additional pedal movement. This is the reality of mixing and matching parts, which means if you feel this may cause an issue, then a power brake package is probably the better alternative.
The last component you need to consider is the brake proportioning valve. This device reduces the pressure to the rear brakes so that, through tuning, the builder can balance the braking effort between the front discs and the rear drum, or perhaps discs, on the rear. Too much master-cylinder line pressure to the rear brakes in a panic stop can prematurely lock up the rear brakes before the fronts. If this occurs, it can cause the driver to lose control of the car. The ideal application is for the rear brakes to lock up only after the fronts have locked. Of course, the ideal stopping distance for any car is with the brakes right at impending lockup.
Parts List B (‘70-newer F-car Drum-to-Disc Conversion)
|1970 Camaro caliper (left)||FRC4060||Rock Auto|
|1970 Caliper (right)||FRC4069||Rock Auto|
|Caliper rebuild seals||WK524||Rock Auto|
|Caliper piston||DPS85010||Rock Auto|
|Brake hose||BH36672||Rock Auto|
|Master cylinder (7/8-inch bore)||MC39027||Rock Auto|
|11-inch rotor||5214R||Rock Auto|
|12-inch rotor (metric lugs)||18A286A||Rock Auto|
|outer tie-rod end (2)||ES2033RL||Rock Auto|
|Wheel bearing (inner)||SET6||Rock Auto|
|Wheel bearing (outer)||SET2||Rock Auto|
|Wheel seal||8871||Rock Auto|
|Wheel bearing washer||618005||Rock Auto|
|Spindle nut||615065||Rock Auto|
|Disc brake prop valve||SUM-G3905||Summit Racing|
|Upper control arm||CNR-423||Summit Racing|
We’ve covered a lot of ground in this story. There is far more to ensure the brake package works as ideally as possible. The big advantage to a disc-brake conversion on early Chevelles is that even a replacement package is a more efficient braking package than the best drum brake ever built. Careful attention to detail will optimize the brake package and create a much safer and more stable platform. And that’s always a good idea.