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I want to boost my all-drum brakes - yes, I just typed that

moparedtn

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1968 GTX, all wheel drums (11" all around) as came from factory.
For now, I was thinking of just installing a booster.
Questions:
1. Do I understand correctly that the boosted all-drum setups used the same master cylinder as the manual ones?
2. Is it really just a simple matter of pulling the master loose from the firewall, removing the little rectangular adapter plate (but leaving the much larger one in place) and installing a booster for all drums?
FSM has this pic of the booster:
booster.jpeg


It appears to me that the connection to the brake pedal is pretty much the same as for the manual brakes? I'd pull the pushrod out of the master I have now, mount the master up to the booster (after adjusting the booster pushrod for zero play) and bolt it down?

Yes yes yes, disc conversion will happen one day as finances allow.
For now, ANY improvement in braking is welcomed, especially if it's as simple as it looks.

Help/advice?
 
Where would the vacuum come from? It would need a vacuum hose connection right? This is relevant to my interests. :) Got a 70' RR with drums all around.
 
On the 68 RR I restored, there was a linkage piece between the pedal and the Booster arm. Actually a 2 part linkage that swiveled like an elbow. There are pics in my RR build thread, But may be a PIA to find that pic, now that we have the new software. My RR was a factory Power Disc car. Also, there will be a port in the intake manifold that can be used/modified or adapted to source vacuum.
RR Thread http://www.forbbodiesonly.com/moparforum/threads/the-golden-rotisserie-chicken.26040/
 
You may also have to change the hard lines from the master to the junction block.the non power lines might be too short as the booster will move the master farther from the firewall.
 
Where would the vacuum come from? It would need a vacuum hose connection right? This is relevant to my interests. :) Got a 70' RR with drums all around.
Most intake manifolds have a provision for this, usually at the back. At least all the 383 or 440 cast iron or aluminum ones I've seen.
 
Your engine also has to produce enough vacuum to operate the booster, can be an issue with aggressive cams.
 
You will need a manifold tee with two connecters if yours has only one.
Where would the vacuum come from? It would need a vacuum hose connection right? This is relevant to my interests. :) Got a 70' RR with drums all around.
Most intake manifolds have a provision for this, usually at the back. At least all the 383 or 440 cast iron or aluminum ones I've seen.

Check. Already have the unused one in the rear of the factory intake; PCV is plumbed under front base of carb now.
 
Where would the vacuum come from? It would need a vacuum hose connection right? This is relevant to my interests. :) Got a 70' RR with drums all around.
On the 68 RR I restored, there was a linkage piece between the pedal and the Booster arm. Actually a 2 part linkage that swiveled like an elbow. There are pics in my RR build thread, But may be a PIA to find that pic, now that we have the new software. My RR was a factory Power Disc car. Also, there will be a port in the intake manifold that can be used/modified or adapted to source vacuum.
RR Thread http://www.forbbodiesonly.com/moparforum/threads/the-golden-rotisserie-chicken.26040/
From what I've been able to ascertain, the disc/drum cars used different boosters than the drum/drum cars - and they used the knuckle link.
Not applicable with mine (drum/drum).
Thanks!
 
You may also have to change the hard lines from the master to the junction block.the non power lines might be too short as the booster will move the master farther from the firewall.
This could be the case. No worries - have flaring tool, will fabricate. :)
Obviously, the master cylinder (which I believe is the same one between boosted and non-boosted drum/drum cars) is going to move forward the depth of the added booster.
Thanks!
 
Last edited:
Most intake manifolds have a provision for this, usually at the back. At least all the 383 or 440 cast iron or aluminum ones I've seen.
Your engine also has to produce enough vacuum to operate the booster, can be an issue with aggressive cams.
Yep. I have around 15hg vacuum now; cam is only marginally aggressive. Should be fine. :thumbsup:
 
I guess my main question is:
Is the rod from pedal to booster on boosted all-drum cars the same as the one from pedal directly to the master cylinder on the manual all-drum cars?
It sure looks like it in the FSM.

Further, how does this booster mount differently to the firewall from just the master cylinder on manual drum/drum cars? Do I remove the big plate on the firewall? Is there a different "plate"?
 
Well I just did a A body 68 Valiant.It had factory power drum brakes.Switched to manual. The booster mounts the same as the masters four bolts.Also had two braces that went to the firewall and to the inner fender.The brake rod from the pedal was different.It was from pedal to clevis to a arm that relays to the booster.Did not change the firewall reinforcement plate.Can't say if the B body is the same.
 
First you should have at least 18Hg of vacuum at idle, it increases on deceleration so don't be fooled by this higher value. Second, you should have a manually adjustable proportioning valve so you can set the front to rear braking bias. Third,
you need a master cylinder matched to the booster in regards to how far the booster rod and master travel. Many have used a regular disk/drum combo with great success as long as you have a proportioning valve for the rear installed. And last, you need the right length of pedal rod and type of pedal for power application. Search "pedal ratio" on the web and you'll understand this concept. It can easily be converted if you research and follow the proper procedures and precautions. You will also need to calculate the output volume of the master cylinder in regards to brake fluid, to the required volume of all four brake cylinders at full stroke. If your borderline, either reduce the diameter of the wheel cylinders or increase the bore of the master. Good luck, love to hear how this works out for you.
 
"First you should have at least 18Hg of vacuum at idle, it increases on deceleration so don't be fooled by this higher value."

Not necessarily so. I run a booster on my car and the motor pulls 12"-13". It worked fine with disc/drum and fine with 4 wheel discs.
 
For improved braking, I got this kit and kept my 11" Hemi Drums on all 4 corners. Straight, smooth, good modulation and performance. Improved shoe material, stronger springs.

www.musclecarbrakes.com
 
On 66-70 b-body the firewall reinforcement plate is different on a power brake booster car than a manual brake car. The hole for for the pushrod is higher on a power booster car. Like has been stated the booster pushrod bolts to linkage that bolts to the pedal. E-bodies also use this linkage.
 
Looks like I need to go find my factory parts manual....
 
FPM open....
drumbooster.jpeg

Drum brake booster.
Y'all know there was a factory retrofit kit they sent to dealers to install on manual drum cars, right? Dealers literally bolted these onto manual drum cars using existing master cylinders.

discbooster.jpeg

Disc brake booster. It has that knuckle joint linkage to the pedal.
 
Disc brake booster. It has that knuckle joint linkage to the pedal.[/QUOTE]


All 66-70 b-bodies power brake boosters use the linkage from the booster to the pedal, disc or drums.
 
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