Need advice for improving brake performance on my 1963 300 Pacesetter

[FWD Look Fan]

The brakes on my 1963 300 Pacesetter were virtually non-operational. It has "power" brakes." (Scare quotes are deliberate...) Four drums, single pot master cylinder. Oh **** braking performance. So, I replaced the master cylinder, all the flexible hoses, the wheel cylinders and the brake shoes. Bled the system unit my knuckles bled. The pedal is firm. Still, when stepping on the brakes, the car responds, "Did you want something from me?"
When looking to change to disc brakes, much research and several calls came up either empty or unhelpful. "Your 1963 is an odd-ball year. Send us your spindles and we'll see what we can do."
Well, that ain't happening.
So, I throw this out to you. Is it possible that the drum brakes be made operational? Did I miss something? Did I get an undersized or defective master cylinder? Or the wrong wheel cylinders? I don't think so, but this is making me doubt everything.
Is a disc brake/dual master cylinder option even available? I don't have confidence in what is being "sold" to me.
I appreciate any help, comments, or empathy from this group of fellow MOPAR masochists. Sorry, I meant, "enthusiasts."
Thanks for any help,
Fwd Look Fan

 

[CBODY67]

Those brakes should be testing the integrity of your seat belts. What brand and type of brake shoes did you install? Sometimes, "brand" can make the difference.

Were the drums machined and what is the ID of the drum. I'm presuming, too, that the brakes are correctly adjusted and you did some harder stops in "R" to ensure the self-adjusters are doing their job?

In theory, you should get the brake shoes arc-ground to match the diameter of the drum's shoe contact surface, to ensure that the whole lining is touching rather than just one high spot. If you have the "Center Plane" brakes with two wheel cylinders/wheel, that might be less important as that more-total contact is what that design is all about.

Can you hear the booster "taking a breath" when you step on the brake when stopped and the engine off? Or once the reserve in the booster has been depleted, with your foot on the brake as the engine is started, can you fell the brake pedal depress itself even more as the engine starts?

The wheel cyl piston diameter should be inverted-cast into the sides of the wheel cylinders. as I recall.

Upgrades? Finding a dual reservoir master cyl that will fit your car is one thing to consider. Seems like somebody recently had a thread in here about using mid-'70s Cordoba front disc brakes?

I'm not sure how the modern linings impact the old drum brake stopping performance and feel, but another friend had something similar to your situation, until he changed name brands of brake shoes.

Just some thoughts,
CBODY67

 

[FWD Look Fan]

Those brakes should be testing the integrity of your seat belts. What brand and type of brake shoes did you install? Sometimes, "brand" can make the difference.

Were the drums machined and what is the ID of the drum. I'm presuming, too, that the brakes are correctly adjusted and you did some harder stops in "R" to ensure the self-adjusters are doing their job?

In theory, you should get the brake shoes arc-ground to match the diameter of the drum's shoe contact surface, to ensure that the whole lining is touching rather than just one high spot. If you have the "Center Plane" brakes with two wheel cylinders/wheel, that might be less important as that more-total contact is what that design is all about.

Can you hear the booster "taking a breath" when you step on the brake when stopped and the engine off? Or once the reserve in the booster has been depleted, with your foot on the brake as the engine is started, can you fell the brake pedal depress itself even more as the engine starts?

The wheel cyl piston diameter should be inverted-cast into the sides of the wheel cylinders. as I recall.

Upgrades? Finding a dual reservoir master cyl that will fit your car is one thing to consider. Seems like somebody recently had a thread in here about using mid-'70s Cordoba front disc brakes?

I'm not sure how the modern linings impact the old drum brake stopping performance and feel, but another friend had something similar to your situation, until he changed name brands of brake shoes.

Just some thoughts,
CBODY67

Thanks, CBODY67. Much to think about before changing out the whole system. I have run the car back and forth to "set" the self adjusters, but no real difference. The car has single wheel cylinders at all four corners. My 60 New Yorker and my 61 Dart have dual cylinders, that while a pain to adjust "juuust right" work great.
I haven't had a lot of luck with multiple sources/manufacturers of brake shoes. I'll keep at it and tame this beast eventually. I'm going to Carlisle with the car and will look for advice (and maybe upgraded parts) while there.
If you are going there, look for me in and around my Pace Car Blue '63 300 convertible!
Thanks again.

 

[Sixpactogo]

It sounds like maybe your booster isn't up to the task. Probably needs a rebuild. You have replaced everything else. In my opinion, you should have replaced that single pot master cylinder with a dual bowl unit but that more than likely is not your immediate problem.
There are some disc swaps that will work with your car but if you go that route, you will need to upgrade the booster with a dual diaphragm because the single diaphragm unit you have now will not provide enough boost. Plus, you would need to replace the master cylinder with a disc brake unit and replace the distribution block with a proportioning valve because the discs require more pressure than the rear drums want. There are tons of information out there so do your research before you make a plan.

 

[Just Carbs]

I have a 64. The stock drum system works well if the drums are round. Stopping power is not the problem. They have stopped plenty fast with whatever shoes I've put on them. The biggest aggravation is every time an adjuster takes up slack, that side will apply the brakes before the other side. The pressure maintainer valve in the master cylinder is supposed to eliminate that, but might not, and can and sometimes does make the shoes drag.
I put a complete 11.75-inch disc setup from a 78 Cordoba on the 64. The stock 64 booster works very good with the dual master from a 67 C body. I did not and do not plan to install a proportioning valve. I see no need for it on "this" car. The brakes are amazing. As in shockingly good. 80 to 20 straight as can be with no steering input, and I mean right now. The pedal modulation is superb. I can make the tires squeak all the way to a stop from 80 without the hint of lockup. Or just lock them up if that's what I wanted to do.

 

[halifaxhops]

@mobileparts

 

[3175375]

Something isn’t right. You need to do some more digging and inspecting. The lead on the booster is a good one… maybe you also need to get some new shoes and send some love to the brake mechanisms, including the wheel cylinders.

 

[commando1]

BTW, your car is gorgeous.

 

[Sixpactogo]

I have a 64. The stock drum system works well if the drums are round. Stopping power is not the problem. They have stopped plenty fast with whatever shoes I've put on them. The biggest aggravation is every time an adjuster takes up slack, that side will apply the brakes before the other side. The pressure maintainer valve in the master cylinder is supposed to eliminate that, but might not, and can and sometimes does make the shoes drag.
I put a complete 11.75-inch disc setup from a 78 Cordoba on the 64. The stock 64 booster works very good with the dual master from a 67 C body. I did not and do not plan to install a proportioning valve. I see no need for it on "this" car. The brakes are amazing. As in shockingly good. 80 to 20 straight as can be with no steering input, and I mean right now. The pedal modulation is superb. I can make the tires squeak all the way to a stop from 80 without the hint of lockup. Or just lock them up if that's what I wanted to do.

Wow! You should buy a lottery ticket with your luck. With all of the problems people have had mis-matching brake parts, you are one in a million. Seems like everyone else that tries to combine front discs with drum rears and no proportioning valve, have all kinds of issues. I have done some research on these drum-disc swaps and learned there is more to it than just mis-matching parts. I learned that the design engineers have a formula that they use. Drum brakes require about 400 psi as opposed to discs that require closer to 900 psi. They use this formula for designing boosters....4" X 4" X 3.14= 50.24 square inches. X 8 (an 8" diaphragm) =400.9 pounds of force. A dual 8" diaphragm doubles the force to 803.8. I quickly learned why my freshly rebuilt single diaphragm booster could not lock up my front discs. The lessons I learned on that project was the reasoning behind what I wrote in post #4.

 

[FWD Look Fan]

BTW, your car is gorgeous.

Thank you commando1! The exterior is in great shape with tight gaps and good paint. There is pitting on the pot metal bright work above the rear bumper. (sigh) And, just about everyone told me that the wheel covers are wrong. I've "improved" this, with 14" "300" wheel covers (incorrect year) on it now. (I hope to rectify it at Carlisle.) I fixed the clock, sent the radio out for repair/upgrade and am now chasing wires to fix the rats' nest under the dash. I am working to replace the glass fuse block
with a blade fuse block with enough slack in the wires to actually see the fuses without removing the seats and center console and lying on my back on the lumpy floor pans. I also fixed the vacuum heater/vent control and have this on the run.
I hope to post this fix in the future, and it doesn't involve dissecting pop rivets to replace broken vacuum hose pins.
My main issue now is brakes. Everything else can wait.

P.S. All the work and all the headaches aside, I love my 60+ year-old cars!
Isn't this the second best, most fun I guy can have? (Well, maybe a top ten? ... )

 

[Just Carbs]

Wow! You should buy a lottery ticket with your luck. With all of the problems people have had mis-matching brake parts, you are one in a million. Seems like everyone else that tries to combine front discs with drum rears and no proportioning valve, have all kinds of issues. I have done some research on these drum-disc swaps and learned there is more to it than just mis-matching parts. I learned that the design engineers have a formula that they use. Drum brakes require about 400 psi as opposed to discs that require closer to 900 psi. They use this formula for designing boosters....4" X 4" X 3.14= 50.24 square inches. X 8 (an 8" diaphragm) =400.9 pounds of force. A dual 8" diaphragm doubles the force to 803.8. I quickly learned why my freshly rebuilt single diaphragm booster could not lock up my front discs. The lessons I learned on that project was the reasoning behind what I wrote in post #4.

I was sure it would need a proportioning valve. On other Mopar disc swaps I've used the early 90s Dodge Dakota rear brake pressure unloader that responds to the change in rear ride height under braking. That was the plan for the 64 also if it needed anything.
The disc swap for the 64 uses everything from the 78 Cordoba. The spindles, 3-inch calipers, 11.75 disc, pads, hoses.....the whole buffalo. The only "wrong" part was the 64-power booster. I'm thrilled that it works like new money, but not surprised. Go figure.

 

[MoparapoM]

Unless you were previously 'AWARE' of the differences, you most likely installed a full set of sub-standard garbage Brake Shoes. I was a Parts Store Manager for many long years. 90% of the shoes we sold were pure garbage. You can NOT depend on the 'person' selling you the parts to have a CLUE what they are selling. You PERSONALLY will need to be responsible for doing your own 'Parts Lookup' and arriving at the BEST Brand and Part Number for your application.

I realize that's really a 'pain', but if you want the best performance, you must have the best parts....

 

[FWD Look Fan]

Unless you were previously 'AWARE' of the differences, you most likely installed a full set of sub-standard garbage Brake Shoes. I was a Parts Store Manager for many long years. 90% of the shoes we sold were pure garbage. You can NOT depend on the 'person' selling you the parts to have a CLUE what they are selling. You PERSONALLY will need to be responsible for doing your own 'Parts Lookup' and arriving at the BEST Brand and Part Number for your application.

I realize that's really a 'pain', but if you want the best performance, you must have the best parts....

Thanks for the comment. Do you have a suggestion as to where/who has shoes with a clue? Thanks for your help.

 

[MoparapoM]

Thanks for the comment. Do you have a suggestion as to where/who has shoes with a clue? Thanks for your help.

I'm a little out of touch with the aftermarket parts industry, retired in 2018. I looked up your car at NAPA Online and it shoes 11x3 on the front, Part # TS148 and 11x2.5 on the rear, Part # TS174. They only supply one quality level which is dissappointing, however 'in the old days' NAPA didn't sell any parts that were truly inferior. That may not be the case today!

Bruce

 

[Aquaman]

Before starting pump the peddle up. Keeping foot on peddle start the car. The peddle should depress some if there is proper vacuum on the booster when the car starts.