Drums to disk swap, small to big rotors ?'s

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rumblefish360

rumblefish360

I have escaped the EVIL Empire State!
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Hey gang.

I have a '74 Duster w/ 4 corner drums.
I picked up a complete stock disk set up of a '75 Duster. Small disks.
I also have a complete big disk set up off a '79 Doba.
I want to use the big disks from the later year B body ('79) on the stock A body arms and spindles. ('75)

Theres the parts, heres the question(s);

When it comes to the brake hose from the body to the caliper, what is the length I'll be needing?

Is there a stock length I can use?

Is there a problem in in the way the hose mounts to the caliper. As in different style mounting pad, hose end. I could be mistaken, it's been a good 15 years since owning a Duster, but, aren't the caliers mounted in front of the spindle?
The later B body calipers I have are mounted rearward of the spindle.

See the problem I'm haveing?
Thats it. Thanks.
 
The calipers are the same between the 73 up A-body disk brake and the B-body. The only part necessary from the B-body besides the larger diameter rotors are the caliper brackets that bolt to the spindle.

Your 74 Duster should have the new style k member that has the sway bar that passes through it. If that is true then just mount the spindles so the calipers face the front in the stock location and use stock 73-76 disk brake hose. The only reason to swap sides with the spindles and mount the caliper to the rear is to make clearance for the 72 and earlier style sway bar. If you mount the caliper to the rear Aspen/Volare brake hoses need to be used.

NOTE: make sure the calipers are mounted so the bleeder is up or you will have trouble bleeding the brakes.
 
Your 74 Duster should have the new style k member that has the sway bar that passes through it
Click to expand...
Hummmmm, I should have also stated that it's a /6 ready for a V-8 (360) swap. Should that be a problem?
I don't recall it to be. (Just wanna be sure before I leap.)
I gather that I do not have to swap sides with the spindles? OR should I?
Which one would be better?
Both brake set ups are complete.

(Good gravy, I have never asked so many questions before.)

I just went outside and looked. I have no swap bar front or rear. The K-frame is the one that has swap bar that goes through it. Like My '73 Cuda.

Thanks dgc333
 
The 73 up v8 k member will have spool type mounts vs the biscuit mount of the previous years.

I have heard that there is a small geometry difference when you swap the spindles and I have also heard that there is not and that they ar symetrical. If you don't plan to install a sway bar or you are going to use the 73 up style that mounts further inboard on the lower control arm I would mount the calipers to the front just to be safe on the geometry thing. There is no performance advantage to either location as far as braking goes.
 
dgc333 said:
The calipers are the same between the 73 up A-body disk brake and the B-body. The only part necessary from the B-body besides the larger diameter rotors are the caliper brackets that bolt to the spindle.
Click to expand...

Carefull here. I have seen references that claim the piston diameter is different between the A-body and the B-body calipers. This could affect brake balance if you are using the stock proportioning valve. If you plan to use an adjustable prop valve, it shouldn't matter.

Also, there are two types of caliper attachment methods. One type uses pins as sliders, the other type the caliper slides in a groove machined into the mount. So the caliper type must match the caliper mounting bracket. Don't just assume you can just grab any old caliper and it will bolt right in.
 
dgc333 said:
The 73 up v8 k member will have spool type mounts vs the biscuit mount of the previous years. --------------
If you don't plan to install a sway bar or you are going to use the 73 up style that mounts further inboard on the lower control arm I would mount the calipers to the front just to be safe on the geometry thing. There is no performance advantage to either location as far as braking goes.
Click to expand...

I do not have a V-8 K-member. Will use the swap kit on the /6 K-frame for the V-8.

I plan on a set of sway bars.
Mounted up front it is. I think that would be easest since I'll be making use of the stock "A" body spindles, not the later year "B" bodys.
 
I am not aware that the piston bore was different. If you look up the part numbers between the 75 A-body and 79 B body they are different but the 79 Aspen/Volare which has the same diameter rotor as the A-body uses the same caliper as the 79 B body which would suggest that other than a running manufacturing difference they are the same.

All the 73-8x RWD cars used the slider type caliper. The pin type was used before and after that time frame.
 
GotDart said:
Carefull here. I have seen references that claim the piston diameter is different between the A-body and the B-body calipers.
This could affect brake balance if you are using the stock proportioning valve. If you plan to use an adjustable prop valve, it shouldn't matter.
Click to expand...

The plan is A body spindles, caliper mounting bracket and calipers for the large disks from a B body.
I just looked for my (Measuring) calipers. I can't find them at this moment. I'll measure piston diameter sizes between the 75 A bodys and the '79 B bodys when I find them.

GotDart said:
Also, there are two types of caliper attachment methods. One type uses pins as sliders, the other type the caliper slides in a groove machined into the mount. So the caliper type must match the caliper mounting bracket. Don't just assume you can just grab any old caliper and it will bolt right in.
Click to expand...

Thanks, didn't assume. Good lookin out. Ya never know how knows what. (Or what they think they know.) I mentioned earlier that I have 2 complete set ups.
What I have exactly is; 1 from a '75 Duster and 1 from a '79 B body.

Also, I'll be making use of 11 inch drums on the rear. I do have a stock "A" body proportioning valve (from the Duster)
An adjustable may be in the future. I'll see how it acts.
 
dgc333 said:
I am not aware that the piston bore was different. If you look up the part numbers between the 75 A-body and 79 B body they are different but the 79 Aspen/Volare which has the same diameter rotor as the A-body uses the same caliper as the 79 B body which would suggest that other than a running manufacturing difference they are the same.

All the 73-8x RWD cars used the slider type caliper. The pin type was used before and after that time frame.
Click to expand...

Ya know...yesterday, I was talking to a MoPar guy that has 2 Dusters (A 71 and 73) He's the manager at the AutoZone. He found part numbers to be the same on the B and A body calipers in question. I would gather from there that the diameters would be the same.
 
Okay, I had to go look up the article I used as reference. I am certainly not a Mopar expert, so I rely heavily on the technical info I read. So if this is wrong, sorry. :toothy9:

The second variable is caliper piston size. The slider-type calipers used on 1973-‘75 A-bodies used a smaller piston: 2.60" as opposed to the more common 2.75".
Click to expand...
Quote taken from this article - http://www.moparaction.com/Tech/archive/disc-main.html
 
Hummm, got me on that one. I didn't finish with parts collecting yet. I think that would be a good idea. (?)
 
An all drum brake master cylinder has equal size reservoirs for both the front and back. The disk brake master cylinder has a much larger reservoir for the the disks on the front. The addtional volume is needed as the pads wear the caliper piston moves out and the internal volume increases. With drums the adjuster opposite th wheel cylnder makes up the clearance as the shoe wears and the pistons stay in the same relative position.

It will work if you don't swap but you will need to be topping up the master cylinder all the time.
 
Thanks dgc. I figured it would work, but how well it would was/is an issue that I not thought out. I'm running a mental list of parts for this.
(Pencil and paper are really wonderful items to have...:sad5: , should have used it here. I do for everything else. #-o )
Hopeful to start soon, but we'll see. Problems with the Magnum first.
Gotta get that up and running first so I can dump the '95 :angryfir: Concord.:sad3:
 
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