A-body disc brake swap

[Karl43]

I need to do some major suspension work to my '68 Barracuda. While I am under there I am considering converting to disc brakes. I have called three vendors that offer disc brake conversion kits and have a few questions.

MP brakes wants $300 more for their kit. Their proportioning valve mounts under the master cylinder and you have to fabricate lines. One guy also commented that MP brakes uses GM parts adapted for Mopars.

SS brakes says their prop valve mounts like to stock one, but I may have to rebend lines from the master to the prop valve.

The last guy that I spoke to told me his kit workes with the original drum prop valve and lines.

Who has used these kits? How did the installation go? These guys claim that you buy their kits and supply brake fluid and grease and in 6 hours - Wham disc brakes no problem.

Is the spindle different for drum and disc brakes? If yes, how do you mount the calipers? One of the guys said that the spindles are not different and they have a braket to mount the caliper to the spindle.

I want to hear from anyone who has done this and how did it go and what did you have to do to get it going. I drive this car everyday and need to drive it into the garage and change it over in a weekend if possible. Thanks for the help.

[ehostler]

Skim through the recent discussions on disc brake conversions. If you have the time to do junk yard hunting, and put it all together your self, I think you will be able to save a little money. You also end up with stuff that can be replaced by your local parts store, if it ever fails).

[451boy]

There is a ton of information on this swap over at the *******.com board in the tech archive. What you really want is the disc swap article from Mopar Action published a while back. Do some web searching and you'll find it. Check out November edition of Popular Hot Rodding now on the newstand and you'll see some more info.

Basically the best way to go (best brakes, cheapest price) is to find a set of '73 to '76 A body disc brake knuckles and use them. The later style brakes are much better than the early style but you will need to go to the big bolt pattern wheels.

There are also a couple of books out that cover Mopar susension upgrades. Tom Condrans book is super good and I highly recommend it. It covers this swap in detail.

[goldduster]

Also, if you decide to got to the '73-'76 Discs, you will need to grab the upper control arms for the swap. Also, if you have a front sway bar, you will have to swap the spindles side-to-side to make the calipers rear mount. This will cause problems with the brake hose, but This Page may help you with that.

[Karl43]

Thanks for the info so far.

I want to go with the 4" bolt pattern four piston caliper system as I have an 8 3/4 axle with the 4" bolt pattern and do not want to get into changing the bolt pattern. 3.23 Sure Grip - really gets through the snow up here in the winter.

[goldduster]

Well, the Stock style 4" Kelsey-Hayes system's parts are expensive...Be prepared to spend $100/ea for rotors instead of $40 for the Big bolt kind. Also, because they are 4-piston calipers, rebuilds/rebuilding are a lot more. Pads also cost a lot more too.

Winter? Don't tell me that you actually drive it in the winter...

[451boy]

I'd highly recommend ditching the 5x4 bolt pattern unless this thing is just a pampered car to putt around in. The 5x4 is dead and parts for it are just going to be harder to get in the future.

You can't buy a really good brake system for the 5x4, best you can do is 11 inch rotor. Wheels for the 5x4 pattern are tough to find in a decent size and so are a lot of other things.

Once you make the move to 5x4.5 then the world opens up.

[dusterbd]

i know people on both sides of this debate. my buddy ed swears by the small bolt stuff, as all he runs are 14 inch cragar ss and rallyes. he says that the 4 piston calipers give him better feel and stopping power, not to mention that he doesnt have to mess around with the rear brakes and bolt pattern.
i, myself, just made the swap to big bolt. i feel no stopping difference between the two systems, really. i like tha fact that the parts are easier to come by, and that i can actually put 15s on the car now. by and large, though, i feel no real difference between the two systems so do what appeals to you. after all, its your car.
mike

[451boy]

Well the polite thing to say is always "do what you want, it is your car." On the other hand, since I'm an engineer I tend to look at things from an engineering standpoint. From an engineering standpoint the 5x4 bolt pattern and 14 inch wheel choice looks pretty stupid. It is 2001 not 1967. A car that has any performance potential at all needs to be running 16 or 17 inch wheels. Not a lot of Z rated 14 inch tires on the market!

Of course, if a guy just wants to drive over to the park and polish the chrome a bit then I suppose 14 inch rims will get you there and back. But don't try to keep up with the Mustangs or Camaros, not to mention the Civics or Supras. They'll bury you.

[dusterbd]

valid points. i guess it would depend on the use of the car. you can get big inch wheels made to fit small bolt, but its really expensive, and you dont have much of a selection (as far as i know).
mike

[DusterBill]

I've got the SS brakes kit (mostly) on my 72 Duster. You do not need to replace the drum spindles, but you do need to drill out one of the bolt holes for attaching the spindle to the lower ball joint. The rear lower bolt hole is threaded and the threads need to be removed.

The kit is pretty simple to install. If well motavated, and you don't run into any suprises, six hours is possible.

The calipers mount to a provided mounting bracket that is bolted on the spindle. A spacer that slides over the spindle is used to locate the disk on the spindle.

The MP kit provides new spindles, and splash shields for the disks. SS brakes has no splash shield to keep water/snow off the disk.

I belive that both kits use the original proportioning valve, but add an adjuster to control the pressure for the rear brakes.

Problems I encountered:

Was sent the wrong spacer. The A-body spacer is a mostly hollowed out piece to slide over the shoulder on the spindle, the b-body spacer is solid and about 1/4" thick. (It took a month to figure out the problem after I had tried four sets of rotors because SS brakes said nothing else could be the problem)

The brake line connecting the two sides of the caliper needed to be bend to fit in the 14" wheels.

Overall I think the SS brakes kit is fine, but I might go the MP route to prevent from having to drill the bolt hole in the spindle so that I could put the drums back on if I wanted to at some future date.

[Hybridized]

Originally posted by 451boy
Well the polite thing to say is always "do what you want, it is your car." On the other hand, since I'm an engineer I tend to look at things from an engineering standpoint. From an engineering standpoint the 5x4 bolt pattern and 14 inch wheel choice looks pretty stupid. It is 2001 not 1967. A car that has any performance potential at all needs to be running 16 or 17 inch wheels. Not a lot of Z rated 14 inch tires on the market!

Of course, if a guy just wants to drive over to the park and polish the chrome a bit then I suppose 14 inch rims will get you there and back. But don't try to keep up with the Mustangs or Camaros, not to mention the Civics or Supras. They'll bury you.

Oh I see, put on some 17" wheels, chrome dual wipers, coffee can exhaust tip(s), Superbird tailfin, and Type R all over the car and you too can keep up with Civics or Supras.

Please!!!!!

Z rated tires, um lets see, how often do you go over 130 MPH? How many of you ever been to that speed? Guess what happens to you on that joy ride when Jonny Law buzzes you at that speed?

BTW with bigger rims, there is more moment of inertia, so it is harder to accelerate a 17" rim than a 14" rim (with the same size tire diameter.)

The 16" and 17" rim have tires with less sidewall depth, less tire flex, better for handling.

But on a 68 Cuda, I'm sure there are a lot more weak links in the steering/front suspension than a 14" rim.

[Karl43]

Thanks for the info dusterbill. This is what I was looking for to help weigh my decision.

Has anyone done the P-S-T kit? How well does it bolt up.

451 boy. You have some valid points, but I am not trying to run circles around the new cars. I am an engineer also and use the car as an every day driver and I realize that I need better braking than drum brakes can do. I don't want to go all out and redesign the whole car. I just wore out my upper control arm bushings and upper and lower ball joints and tie rods. I figure since I have to replace all of that I might as well look into disc brakes. I can hold my own against them in a straight line.

Yes, it is a 68 Barracuda fastback. I do drive it everyday because I do not like the new cars available today. The fastback Barracudas are the first sport utility vehicles - they were just two wheel drive. This car is my yellow one which is a plane Jane 318 Barracuda. I drive this one because I do not want to drive my 68 340-S with original paint, and my '67 Formula-S 273 4bbl practically fully loaded: PS, PB, A/C, console, tach, buckets, bumper guards, hood mounted turn signals, and trailer tow package - $4200 sticker price, I have the original sticker from the original owner.

So I drive the 68 plane jane every day so I can preserve my Formula-S cars. It is more reliable and fun to drive than new cars. This car has about 400,000 miles on it - I want to see if I can get it over 500,000 miles.

I also have a 66 Valiant Station wagon I am building at my dad's house for the nest driver. It was a slant six three on the tree car with only a electric window wipers. I am converting it to a Formula-S suspension, 8 3/4 axle with 2.76 open gear, dual reservoir brakes and a 318 4-bbl, and try to convert it to A/C. A cruise control would be nice also.

[kekoakeakane]

The P-S-T kit went in well. Myself and another person that I know of had problems with the lower ball joints hitting the 11" drum brake backing plate. I'm not sure if thats a problem with the disc brakes. PST sent me new lower ball joints which fit. The other guy was able to find lower ball joints at the local parts store, so PST refunded his money for the ball joints.

All the other parts went in smooth as can be considering it's suspension work on 30 year old parts. No kit that I know of includes the pitman arm, but it's not a bad idea to replace that while you're at it. As far as special tools are concerned, you'll need the upper ball joint socket and 3/4" breaker bar, pitman arm puller, roll pin punch helps with the pin in the strut bar, pickle fork (no need for finese since you're replacing all the parts anyway). Hopefully, you're lower control arm shells aren't as eaten up as mine were and you can re-use them for the poly bushing. BTW, the recommended method for removing the rubber from the LCA bushing is to burn them out. I, on the other hand, had to chisel out the old ones and press in new ones (which were included in the super kit). The sway bar bushings that are included don't include the brackets so if you're curious about how to replace those, then look at this thread: Replacing Sway Bar Bushings .

The super polyurethane kit took myself and a friend about a full weekend plus to install. Hope this helps.