Golden Goddess heart surgery

[ckessel]

Like this?

 

[GetX'd]

It’s been a while, but time to get back on it. New brake pads, all new rear brake hardware, including self adjusters, and smaller bore wheel cylinders. Hopefully I can solve the brake mystery and move on to other things!

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Hey young blood - great to see you’re getting things done w/your X. Looks like Progress is at hand. Keep it up!

 

[Cheapsunglasses]

Beautiful day for brake bleeding…again

 

[Cheapsunglasses]

Aaaaah, keystones, the best

 

[Cheapsunglasses]

Well first drive doesn’t seem good. Drove it a couple blocks to a burger joint, and it didn’t seem better. Maybe the pads need to brake in?

 

[Cheapsunglasses]

So idk if the pads needs broken in, or if there’s still a problem, I still have no brakes. I have a good firm pedal. But still nothing.

I have the Dr Diff aluminum master cylinder, there wasn’t any instructions, but I have it plumbed rear brakes at the front, and front brakes at the rear, like the factory. Can a anyone confirm if this is correct.

 

[qkcuda]

That is the way I plumbed mine. Works fine.

 

[71RRHI]

I love keystones. Growing up my parents had them on their 72 Cutlas. My first car, a 68 charger had them. Wanted to order a set for my 67 Coronet 500 when I took the weld racing rims off. But the back space sizes were very limited. So I ended up with magnum 500's

 

[Kern Dog]

Hey there, I'm just jumping in here on page 29 so forgive me if I missed some details you may have covered. I did see that you have a 4 to 2 bolt adapter for the 2 bolt master cylinder. Was the pushrod in the booster extended enough to compensate for the adapter?

Factory type parts or aftermarket rotors/calipers, etc?

I read that the pedal is firm but the brakes are not satisfactory, right?
After years of multiple combinations, some of them terrible, some pretty good and now excellent, I might be able to help.
The only time that I've had a non power disc/drum system that had a firm pedal and poor braking, that car had a bad proportioning valve. I simply replaced it and didn't dig any deeper as to why the old one was bad. In retrospect, it could have been gunked up to the point where it wasn't flowing enough volume and the 4 corners were not getting adequate pressure.

In my red car, I tried a manual master cylinder setup a few times with these 4 wheel discs and while again I had firm pedal and poor braking, a change
back to the power booster restored the braking force that I wanted. It wasn't the proportioning valve with this car.
The power booster could be bad. One test is to press the pedal a few times with the engine off. With your foot still on the pedal, start the engine. The pedal should sink a little but then equalize after lifting then pressing the pedal a couple of times.
Some brake pads and shoes do benefit from being "bedded in". I've only done that once though even though I've changed pads on my 400,000 mile truck numerous times without ever bedding in any of them. Same goes for every other brake pad or shoe swap that I've ever done. I suspect that this practice is probably limited to the higher performance race type pads.

In my experience, when the performance of a brake system changes for the worse, it comes down to a few things.
Contamination of the pads or shoes. Gear oil, wheel bearing grease, leaky wheel cylinder or caliper, etc.
Reduced pressure at the calipers or wheel cylinders due to leaks, blockages, corrosion or a bad master cylinder.
You can have a firm pedal and still have shitty brakes because the feel at the pedal is only representative of a system holding pressure.
A pressure gauge may be of use to you:

Front discs need 1200 or more, drums are okay with around 600.

Report back soon!

 

[Cheapsunglasses]

@Kern Dog , just to recap, pirate Jack factory type brake booster, and front 11” disc. Factory 11x3 rear drums. Willwood distribution block/proportioning valve. And dr diff aluminum master cylinder with 2 bolt to 4 bolt adapter.

Everything I’ve tried it all seems the same, it’s kinda hard to describe it, or maybe it’s understanding what’s going on. The pedal is nice and firm like a power brake pedal should be, it feels like it’s bled properly, and it feels like the booster is working. But when you apply the brakes it doesn’t feel like they’re grabbing.

I’ve had manual drum, power drum, and power disc cars before, and I’ve had failures with boosters and master cylinders on all those. It doesn’t feel like a failure on any of those components. It feels like they’re not grabbing enough. When I bleed them, it’ll shoot a strong steady stream clear past the other side of the car.


This is kinda what I’m leaning towards. Are you meaning the tip that screws in and out on the pushrod being screwed out more?

Was the pushrod in the booster extended enough to compensate for the adapter?

 

[Kern Dog]

The fact that you're feeling a firm pedal shows that you are probably on target for the most part, how hard is it to just try different pads and shoes? Is availability difficult?

 

[Cheapsunglasses]

I just put new shoes and pads on

 

[Cheapsunglasses]

Idk what was on before, but I put raybestos semi metallic on

 

[Kern Dog]

I wish we lived closer. I have spares of stuff that I swap around when I am not ready to throw more money at a problem.

 

[Cheapsunglasses]

Im starting to lean towards the brake booster being an issue. That’s the only thing I haven’t touched. And yes, when I pump the pedal and start it I can feel the pedal drop slightly. There’s plenty of vacuum for power brakes, and the pedal has felt the same before the cam swap and after the cam swap.

One thing I forgot about is that’s the second booster I’ve put on the car, the first one was bad out of box, and I was on the phone with my buddy and he said he remembers the brakes working ok for a while after putting the new booster on.

Having a firm pedal, I believe the pedal moves about 4”, so I’d think that’s enough movement. But I can stand on the brakes and takes a block to slow down. I’ve swapped everything, except that

 

[Kern Dog]

Last year I installed two of those reproduction 66-70 B body boosters, one in each of these cars:

It improved the braking in both cars tremendously.
My Charger has a bigger cam so I have to use a vacuum pump. With the pump off, the car takes forever to stop.
The problem with failing boosters is that without that boost, you have less mechanical leverage than you do with a manual system so all else being equal, (Master cylinders the same, calipers/drums, pads/shoes) It will take longer to stop a failing power brake car than a properly operational manual brake car.

 

[Cheapsunglasses]

The problem with failing boosters is that without that boost, you have less mechanical leverage than you do with a manual system so all else being equal, (Master cylinders the same, calipers/drums, pads/shoes) It will take longer to stop a failing power brake car than a properly operational manual brake car.

That sounds a lot like what’s going on!

The best comparison I can think of is my 68 satellite with 10” manual drums stopped sooner and better then the GTX with power disc brakes

 

[Kern Dog]

Trying to get accurate information on brake pedal ratios seems impossible. I've seen some respected people state that power is 2 to 1 and manual is 4 to one but by doing the math, my manual setup was in the 7 to 1 ratio.
You are supposed to take the measurement from the pivot point at the right to the center of the pushrod...

Then divide it with the distance of the pivot to the center of the pedal. I had something like 12 3/4" divided by 1 3/4". That comes out to 7.25 to 1.
Power systems don't need as much leverage due to the added assistance of the boost.

 

[Cheapsunglasses]

It’s kinda hard for me to get under the dash, but the pedal travel seems to be as much as any other vehicle I’ve driven. And the pedal sits pretty level to the gas pedal. I’m kinda leaning towards the brake booster

 

[Kern Dog]

All the times I've changed out master cylinders and such, the easiest way to do it really is to remove the seat. I've removed the steering wheel though since 5 Allen screws hold mine in place. It still is a struggle.
You can try disconnecting the vacuum line to the booster and see if the car performs the same. That would show you something. If it gets a little worse, maybe the booster is working a little but not enough.