X Body Disc Brake Swap


Swapping disc brakes for drum brakes is certainly not a new idea. But if your on a frugal buget, disc brake swap kits are a bit too pricey even for "stock" parts. Alternately, the exotic swaps command high prices down the road as well - you can't walk into your local Napa store and get a replacement cross drilled rotor for your Wilwood setup. Not to detract from the quality of any of these companies, they all put out an extremely fine product.

If you happen to be debating to swap or not to swap, just do it. You'll have no regrets. The difference in braking effectiveness is dramatic. You'll be able to kiss all those drum pitfalls away. Pitfalls which you only realize once you've swapped.

Once you've gathered all the parts together that you need, a helper, and the convinience of a shop the entire process will take about five hours, including some cursing along the way. =)

One thing that should be stressed; If you find a donor car, get the parts now. If you wait, theres a high chance that when you go back, the parts will be gone. Prior to my decision to swap to discs, I could find a donor car practically every week I went to the autowreckers. And of course, Mr. Murphy comes along when I do decide to swap ending up in a four month hunt for a donor vehicle.

A word on swap parts. Nearly everything 'consumable' is available new or rebuilt. Master cylinder, calipers, rotors, caliper bolts, seals, bearings to name just a few. One of the benifits of using stock parts. The choice will be yours wether you use the donor parts on your car, or use the donor parts for cores. Prices are very reasonable I found. I elected to go with the rebuilt and new route for a number of things, master cylinder (got a really nice dual bail unit from the rebuilder), new rotors, rebuilt calipers, new caliper bolts, and mandatory (its a small price to pay for your safety) new flex lines. Of course, the condition of the donor parts will play a large factor in which route you go, weigh your options and determine if its worth using the donor master cylinder, realizing you might end up replaceing it sooner than later. All told, I paid $609CDN for components, including the initial price for the donor parts (1992). At that time, a U.S. supplier of a swap kit was asking around $900US, add exchange rate, duty and taxes to get it into Canada and the final price just sitting in boxes would have been in excess of $1200.

Suitable Donor Vehicles

Note: 1967 and 1968 Nova/Camaro disc brakes use the 4 piston caliper. It is recommended to use the 1969 and up single piston calipers. I'd like to thank Don Coffman of the Golden State Novas for bringing this to my attention.

As you've probably noticed, all of the above, save the Camaro and Firebird, are X-bodys. However the first generation F-bodys share the same subframe with the X-body lines.
You've also probably heard tell of using other vehicles, such as Chevelles, Monte Carlos, and Tempests for the job. Well, yes it can be done, but you will have some extra work ahead of you, including a search for proper backing plates. Also, theres an issue about ball joint size. They're different, which translates to even more work. And one more factor, X-bodys are "rear" steer. G & A Bodies are front steer, you'll need to swap the steering components around side to side. The KISS principle goes a long ways when doing swaps.
You might also be asking about late model X-body disc parts (1975-1979). Forget that to. The spindles are taller, are one piece, and are front steer. If you happen to be doing a swap to an earlier front steer (A-body or other similar mid/full-size), the late model one-piece spindles still pose the geometry problem of being taller. One new note, for the fullsize front steer swappers, there is an aftermarket supplier of tubular upper control arms to compensate for the taller late model one-piece spindle.

Donor Parts Required

If Swapping from Manual to Power Brakes;

Depending on the yard, most will just torch out entire assemblies, and you get everything. With the master cylinder, the prop. valve braket bolts on with the same bolts. And the small hard lines linking the prop. valve to the m/c effectively give you one piece. Just remember to tell them you want everything that attaches if you're not doing the removing.
One important point is to cut the lines running to the brakes and retain the flare fittings in the proportioning valve. Once you get into the swap, you will find that the line feeding the rear brakes has a different sized flare fitting (but the same sized steel line). Probably the factories way of preventing incorrect prop. valve installation.
And on the other end of things, the spindle has the caliper, rotor, backing plate, and all other bits that make up the assembly, as with most yards, they'll torch through the control arms and you'll get the entire assembly. Just don't assume anything when dealing with a yard. Some guys give you every nut and bolt (speaking of which, keep any bolts, clips etc. you remove at the yard, if you need them you have them. If you don't, add them to the misc. fastener bin.) Other guys will undo everything and give you only what you asked for.
Once you get everything home, you'll find that a lot of stuff seems identical to the basic drum setup. And for the basics, it is. You will also note one item: The disc and drum spindle is identical. Almost. =) The top mounting pad of a disc spindle is machined down a half inch. Yup, we go through all that trouble to find that the basic guts of the two are the same part. So why bother finding a donor? Lets just say, Caliper brackets and backing plates are not to be found at any autosupplier. However, the aftermarket has recently, added caliper brackets and backing plates to their line of individually priced parts. But then, you'll need to buy those at a few bucks, pay someone to machine the spindle if you can't do it yourself, and have your car stuck on jackstands for an extended period of time while you run off to the machine shop with all the parts so they can verify your caliper will be square to the rotor.

Common Disc/Drum Parts

Pre-swap Prep

Time to disassemble, clean, and paint the various parts you'll be using. You'll notice everything is bolted together, from backing plate, to steering knuckle, to caliper bracket. Take it apart if you wish, and give it a detailing job. Nows the best time to get it done.
Now is also the time to check the condition of various parts, and determine which rebuilt or new components you want. If in doubt, replace it. No sense taking any chances with safety. Yours, or the kid running into your path.
Evaluate the condition of you present ball joints, best to replace them if neccessary while things are apart.

Some 'Special' Tools You'll Need

Some Other Stuff You'll Need

Basic Swap Process

Time to get dirty. Start at the wheels. You'll basically be knocking out the old spindle, and replacing it with the disc brake spindle. Remember, you've got a coil spring tucked up in those control arms--follow the safety rules for changing the coil springs. Undo the tie-rod end and brake line. Remove the old spindle. Change ball joints if required, and bolt in your new spindle. Reattach tie rod end. Procede with the bearings and rotor. The flex line will not bolt in like the donor vehicle. Disc vehicles have the hard line pointing towards the outside and bolted to the lower control arm with a bracket that is supplied with the flex line. Drums have the hard line bent at the top of the frame rail pointing to the ground. Not to worry however, the flex line bolts right to the hard line, and the caliper end you can improvise. Typically, a simple u-shape, leaving that flex line bracket unattached. If possible you might be able to unbend that bracket and discard it. If not, it does not (in my case anyway) hang in such a way as to provide a snag point for road hazzards.
Repeat the process for the other side of the vehicle.
Into the engine compartment.
Remove your old master cylinder and prop. valve. Bench bleed the replacement m/c. Install m/c and disc brake prop. valve. Heres where you find out which of the original hard lines fit the prop. valve. If memory serves me correctly, the fitting for the rear brakes will have to be replaced with the salvaged fitting. Remember, brake lines get double flared. You'll also need to do some re-routing (bending) of the brake lines to fit. After an exercise in cramped quarter flaring, bleed the brakes, check for leaks, and have a stopping good time!

Working on a 1st generation Nova? Take a look at Pat Cosseys 1967 Nova disc swap pictoral.

Remember to employ all safety precautions when working on any vehicle.
This information is only intended as an overview and may not include all the necessary information, data, or facts to complete the swap.
Remember, every vehicle is unique, and research for your particular vehicle is recomended.

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This Page Created By Alexander M. Bilan (gmguy89@netscape.net)
All Rights Reserved
January 29, 1997
Revision 2.6 April 2,1999