Swapping Late-Model Vented Disk Brakes Into Your AMC

By Jeff Barfield <jrbarfield@mindspring.com>

 Using these instructions you should be able to convert any AMC with front

drum brakes to front disk brakes.  Anyone who has done some brake work and

has a reasonable amount of mechanical knowledge should be able to perform

this swap.  When you read in the instructions "bleed the brakes" if you

don't know how to perform that function stop now and get help from someone

with more mechanical experience.  These instruction assume that you know

enough about brakes to properly bleed them, check for leaks and test their

stopping power in the driveway before going out on the highway.  If the

previous statement in not true for you stop now and get assistance.  David

Crooks said it best in a response about this message:

 "If you're not well versed in brake systems get help from someone who is.

If you modify your brake system you could be liable if it fails and you 

hurt someone or destroy property.  Brakes aren't difficult to work on, once

you've been taught how, but they're one of the most important parts of a

car, and deserve a lot more respect than they usually get."


 Parts you will need from a donor car:

 	Rotors Including Bearings

	Spindles Including All Bolts Nuts Etc.

	Backing Plates

	Caliper Mounting Brackets and Mounting Bolts

	Proportioning Valve

	All Front Metal Brake Lines

	Power Booster Including Check Valve (For power brake systems)

 Parts you should buy new or rebuilt (You can take these from the donor car

but unless you know it to be a good system I would not):

 	Master Cylinder

	Calipers (These are cheap for rebuilt ones approx $20.00 each)

        Front Flexible Brake Lines (Kennedy American had these on special

          for under $20.00)  Replace these, do not reuse old ones.

	Brake Pads


 Find a donor car, almost any 71 and up AMC with front disk brakes will make

a good donor car.  I highly recommend that you not use the four piston

caliper setup from 70 and down disk brake cars, (instruction are included 

to swap this older type to the newer type) they are far more expensive and

harder to maintain and from what I am told they just plain don't work as

well.  There were 2 types of single piston caliper systems used in 

different years, not sure which was used when, but there were Kelsey Hayes and

Bendix systems, some people prefer one system some the other, both work well

and the instructions provided here will work for either brand.  Be sure that 

you know what kind of car that you used for a donor so that you can order

brake parts later.

 Remove all parts listed above from the donor car (take the calipers for

cores if you are buying rebuilt) this should be fairly simple and self


 Be sure to make a quick drawing of the proportioning valve and where each

line runs from each connection in the valve, when you go to install it you

will be glad that you did.

 I have been told that there were 2 different proportioning valves used that

had different pressure ratios front to rear, to assure that you have a

correct one for your car be sure that the donor car is of similar weight,

(Ambassadors and Rebels will use one while Javelins, Concords, Gremlins,

etc. will use the one for lighter cars)  If your donor car is of the wrong

variety to use the proportioning valve of the donor car you may look for 

the correct valve from another car (don't know if they are available new or 

not) or you may purchase an adjustable valve.  If you choose the adjustable 

valve you should have a brake expert adjust it for you I would not attempt

this myself, misadjustment is asking for trouble.

 Also there is a short metal line going to a double female sleeve and then 

to the rear brakes, be sure to get this line and the sleeve, if you do your 

old rear brake lines will connect right up.

 Have the rotors turned and checked to see if they are in specs.


 Remove the drums and all brake hardware from the car.

 Disconnect the metal line from the flexible line that runs to the wheel

cylinder, this can be difficult flare wrenches may help or in my case I had

to resort to vise grips.

 Remove the nuts holding on the backing plate and spindle.

 Remove all the bolts, there is a gotcha here one of the lower bolts may 

hit a 90 degree turned spacer between the lower control arm and the strut rod,

save yourself the hour I spent removing the strut rod and stripping a bolt

and take a hacksaw and cut off the bolt, you can use one from the donor 

car. Since the bolts come in from the front on the disc system this will not

be a problem in reassembly.

 Remove the master cylinder, power booster and all front metal brake lines 

as well as the brake pressure warning unit.


 Install the spindles, backing plates and mounting brackets, if you watched

how everything came off this should be easy.  The calipers should mount

toward the top front of the rotor.

 Mount the rotors onto the spindles and secure the bearings with the washer,

nut and cotter pin and put on dust cap.

 Connect the new flexible brake lines to the calipers, another gotcha here,

if your car is equipped with the loveable trunnions, like mine, then the

metal part of this brake line may want to run right through the middle of

your trunnion.  I overcame this problem with a tubing bender, if you have 

to do this connect the line to the caliper first then bend the brake line

down and toward the middle of the car to run behind the trunnion.  Bend it a

little at a time and keep setting the caliper in place until the line is no

longer touching the trunnion.  Others have told me this was not a problem

when they did the install, I have to assume that the brakes lines come out

of the calipers at different angles depending on who manufactured the

calipers you are using, if you don't have this problem it will save you

about an hour on the install.

 Install caliper with brake pads.

 Connect the free end of the flexible line to the mounting plate inside the

wheel well.

 Install the power booster from donor car being sure to connect the vacuum

line, this is an excellent time to clean it up and paint it.

 Install the master cylinder and be sure to bench bleed it first.

 Run all the metal brake lines that you removed to their appropriate places

and connect securely, do not mount the proportioning valve yet, let it hang

by the brake lines until you have finished.  The brake lines may require

some custom bending to mount to the firewall but this isn't too difficult,

just be careful not to crimp or break them.

 Once you have the brake lines securely fastened then secure the

proportioning valve inside the engine compartment.

 Lastly bleed the brakes on all four wheels, check for leaks, and test for

stopping power.

 Please also note that for true balance on the brakes the braking system 

with disk brakes were designed to be used with 10" rear brakes which I

believe came on all disk brake equipped cars and all V8 equipped cars, the

I6s with front drums, came with 9" rears.  There are some people running disk

front with the 9" rear brakes and working fine, but to accomplish optimum

balance between front and rear if the rear brakes are not already 10" drums

these should be swapped as well (this swap is not covered here).

 Many people also mentioned the swap of early disk (70 and back four piston

caliper non vented rotors) to late disk (71 and up single piston calipers

with vented rotors).  This is accomplished the same as above except the

master cylinder and power booster are identical to the later model cars and

the proportioning valve and metal brakes lines should work just fine.  All

parts at the wheel including spindles, backing plates, mounting brackets,

calipers, rotors, and flexible brakes lines should all be replaced as 



Jeff Barfield


69 Javelin SST 343  (Now with disc brakes)


 Jerry Casper (GremlinGT@aol.com) adds: I went thru my Carlisle-acquired 

book called Motor Crash Estimating Guide to find out how much the front hubs

interchanged. Apparently all 70-78 AMC drum hub bearings and all disc brake

hub bearings are the same size, so even if the other parts don't line up, I

"should" be able to use any AMC hub from those years to get this Pacer

rollin', supposing I actually am able to acquire it. I don't see any

reference to Bendix brakes, though, and they don't list the spindle itself,

either. But the bearing size should be the best indicator anyway, so I"m

going with that assumption.   And since I went to all that trouble, here's

the list I created for the front drum and disc brake interchange, complete

with part #'s:

  Front Hub and Drum

   6 cylinder:

      3219569 - 74-78 Matador, Ambo, 70-74 V8 Hornet, 70-73, V8 Gremlin, 

                75-80 Pacer

      3153621 - 70-72 Hornet, 70-72 Gremlin

      3219568 - 73-76 Hornet, 73-76 Gremlin

   8 cylinder:

       3219570 - 74-78 Matador, Ambo SW 6-cyl, SW

                304/360/401, 75-76 Hornet, 74-76 Gremlin

 Front Disc and hub

     3210408 - 74 Matador, Ambo, 71-74 Hornet, 70-74 Gremlin

     3229565 - 75-78 Matador, Ambo, 75-76 Hornet, 75-76 Gremlin, 75-76 Pacer

     4488470 - 70 Hornet

     3229048 - 77 Hornet, 77-78 Gremlin, 77-78 Pacer

     3250578 - 79-80 Pacer


   Drum:  Inner - 3141139

          Outer - 3141140

   Disc:  Inner - 3223343

          Outer - 3223345

 That's all for now. I'm gonna have to acquire some more of these Crash

Estimating guides, they're great reference material. Even list the decals

like Levi's and Cassini for the fenders and their part #'s.


NOTES from Andrew Hay (adh@an.bradford.ma.us):

 Bendix 2, 3, and 'delco' mix-n-match parts like rotors and pads.

 2a seems to be the same caliper as 2 but thick pads and thin rotors.

 Bearings are listed as 'timken set 6 inner, set 2 outer' for -all- drum and

disk '58-'83 -except- '74-'78 Bendix, which take 'set 17 inner, 16 outer'.

 Oil seals are listed as 47523 for '74-'78 Bendix, 46130 for all other disk

and drum.

Spindle Interchange:

Pre-70 4-piston Bendix

70-74 Kelsey

74-78 big Bendix

77-79 4-cyl Bendix [thin rotors]

77-8? Bendix

and probably a host of others...


NOTES on PROPORTIONING VALVES from David Crooks (dcrooks@nortel.ca)

Frank wrote:

>  THE POINT: It is best to leave the original "proportioning valve" in the

>  older, pre-70 cars (I don't know exactly when a real proportioning valve

>  was used), but make sure you change the master cylinder.

 Real proportioning valve's were used earlier than 1970, as my 69 TSM shows.

The difference was that they weren't combined with the pressure switch to

make the combo design until later.  According the the book, the

proportioning valve was only used on cars with front disks, and was located

on the body side sill just ahead of the rear axle.  The valve limits the

pressure going to the rear brakes to 200psi on the lighter cars (AMX,

Rambler etc.) and 400psi on the heavier ones (Rebel, Ambo etc.).

 There's more to it though.  A brake system should be balanced.  If the

back's lock up to fast, you're going to be in trouble.  If the back's don't

come on strong enough you're not stopping as quickly as you could.  Cars

equipped with front disks also got Bigger rear drums, to help maintain this

balance.  If you're going to swap front disks onto an all drum car my two

cents are:

 You must swap the whole front assembly, spindles, rotors, caliper mounts, etc.

 You must swap the master cylinder assembly (no check valve and a bleed

hole for the fronts to prevent residual brake line pressure)

 You should also swap the rear brakes (i.e. drums, cylinders etc.) to the 

larger size used with the front disks.

 This last may be a problem, as the rears don't swap as easily as the fronts.

 If your donor car is the same size/weight as your receiving car then swap

the proportioning valve.  If your donor is different than your receiving car,

get an adjustable proportioning valve.  These are available on the after-

market from many sources, and will allow you to adjust your brake balance. 

 I'll be learning more about this, as I'm currently hunting up a donor

vehicle to convert my 70 Javelin to front disks, and will post any other

suggestions I come up with.

---------------------- end of tech tip -----------------------

Jeff Barfield


69 Javelin SST 343

AMO #2550

Peach State AMO


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