Which 7/8 master cylinder?

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The firewall side should always go to the front brakes........in a disc/drum system. This makes the rear brakes the emergency back-ups

If you hook it up reversed, and the rear brakes go out of adjustment, but not a hydraulic failure, then the pedal will travel lower and lower over time, andno braking will occur in the front system until very late in the pedal travel. If the fronts have any little problem, you may not have enough pedal-travel to affect a good stop.
Whereas hooked up properly, this is an unlikely scenario.
>>If the M/C was not properly bench-bled, and a pocket of air remains in the hydraulic pressure transfer chamber, (the chamber between the pistons), this would cause excessive pedal-travel and "poor braking"..... because the rearmost piston would have to compress that air before achieving some kind of hydraulic loc-up, then the front most piston would have to do it's thing; moving the rear shoes out to the drums, and then braking could begin at both ends.... but that is gonna take a lot of pedal travel. But
If the front brakes are hooked to the frontmost port then three things may happen; 1) you run out of pedal-travel, and 2) the rear brakes will never work, and 3) the front brakes will be spongy, and may/will work "poorly" .
For these reasons, I prefer the tear-most piston to be plumbed to the front brake system...........................but
>>for all this to work correctly, the rear-most piston has to park as close to the firewall as is physically possible. This ensures that the Compensating port is always open when parked, and the chamber is full of fluid. If your pushrod is too long, closing the port, then, over time, the pedal will not return to it's fully up position, and pedal-travel will become excessive, and eventually , you will run out of travel.It will however work fine for the longest time, until the pads become worn enough that you notice the stinking low pedal.And if a minor leak,or a seep,developes while the port is covered, the system cannot replenish the lost fluid, and you won't know about the seep until one day you wonder why your brakes are so poor, and the M/C is still full of fluid!

>> And here's a wild card
If you M/C is equipped with a piston stop for the frontmost piston, and you installed it wrong, driving the bolt into the front piston,instead of behind it then:
The rear brakes cannot work, and
When the rearmost piston hits the front one with the mechanical transfer system, it will stop moving. The pedal will sorta feel like it's supposed to, but perhaps only a small amount of fluid went out to the calipers and so they will be only partially engaged...... and so the Brakes will be "poor".

The same can be said for a M/C that does not have a front piston stop, But the internal stop system has failed siezed, or the fluid is not going out to the rear brakes...... as in somebody put a clamp on the rear flexline,lol..Altho if that was done with the pistons properly parked, then the front system would almost instantly be engaged, as soon as the C-port was covered, with the slightest pedal travel
These are both/all highly unlikely scenarios.
That's all I can think of for now,lol.
 
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Just talked to the tech desk at wilwood. They said on the 2 the master cylinders(7/8 and 1") that the primary port is the farthest from the firewall??????? So the front brakes go to the front (radiator side) port. Does this sound correct???
 
71Demon said:
Just talked to the tech desk at wilwood. They said on the 2 the master cylinders(7/8 and 1") that the primary port is the farthest from the firewall??????? So the front brakes go to the front (radiator side) port. Does this sound correct???
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Not to me.
Did they give a reason for their backwardness?
But internally,the pistons are or should be,the same size; so the calipers won't know the difference.
But you will have to plumb your Combination valve differently.

But on a disc-drum system, I would sure want to plumb it the way Chrysler did.
 
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AJ/FormS said:
Not to me.
Did they give a reason for their backwardness?
But internally,the pistons are or should be,the same size; so the calipers won't know the difference.
But you will have to plumb your Combination valve differently.

But on a disc-drum system, I would sure want to plumb it the way Chrysler did.
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No they didnt and I should have asked I guess. but I agree with you.
 
Wilwood master cylinders are configured for Chevy applications. The front port feeds the front brakes and vise-versa.
 
If you are running a Wilwood master cylinder, the front port must feed the front brakes regardless of the application.
 
would it work just as good then if its plumed front to front? or is there an advantage or difference to having it done back to front brakes with a mopar MC?
 
Yes. The front brake reservior is always larger than the reservoir intended for the rear brakes, regardless of application.
 
AJ/FormS said:
I bet your M/C has two different chamber sizes . The bigger chamber goes to the calipers.
OOps missed it by that much,lol
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Im hoping my problem isnt the new disc brakes on the rear. car stopped fine with front disc and rear drum.
 
Here ya go, here's why I don't like the front piston going to the front brakes.
If you get the pressure transfer chamber full of air, only the rear brakes will work, and the braking will be poor.
I think you are gonna have to re-bench bleed that puppy.

If that don't cure it, then you will have to take it apart and make sure it was assembled correctly.
If it was my M/C, and it had a big and a little reservoir, I would interconnect the chambers about half way down, and then I would plumb it like a Mopar, IF IT WAS MINE, and then I would check the fluid level more than once a year,lol. I like knowing that the front brakes are directly activated by my foot.

 
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AJ/FormS said:
Here ya go, here's why I don't like the front piston going to the front brakes.
If you get the pressure transfer chamber full of air, only the rear brakes will work, and the braking will be poor.
I think you are gonna have to re-bench bleed that puppy.

If that don't cure it, then you will have to take it apart and make sure it was assembled correctly.
If it was my M/C, and it had a big and a little reservoir, I would interconnect the chambers about half way down, and then I would plumb it like a Mopar, IF IT WAS MINE, and then I would check the fluid level more than once a year,lol. I like knowing that the front brakes are directly activated by my foot.

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Bingo!!. That sounds like my problem. It does feel like only the back brakes are working.
 
Is it possible Im introducing air back into the front(radiator side) primary port (front brakes on wilwood) after its bench bled by bleeding the back brake lines first? or is it even possible to get air back in the master after its bench bled while pumping to bleed the lines?
 
71Demon said:
Is it possible Im introducing air back into the front(radiator side) primary port (front brakes on wilwood) after its bench bled by bleeding the back brake lines first? or is it even possible to get air back in the master after its bench bled while pumping to bleed the lines?
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Yes it is
That is why the M/C usually comes with the little plastic fittings and cheapo rubber or plastic lines. The idea is to keep the lines submerged during the procedure, and if you see fluid going back up the lines, you have to pinch the line to prevent that, else you'll just be shuttling the air back and forth.
The compensating ports are at the rear ends of the chambers, so I drop the front down a hair while just tickling the pushrod. When the tiny bubbles stop coming out, then I elevate the front end and continue, until no more air comes out. I pinch the lines on every back stroke, to make sure the pistons have to suck in fresh fluid through those little tiny ports.
Once that's done and the m/c is mounted back up with the lines back on; then you still have a little pocket of air to get rid of right inside the outlet ports. I have a helper push down on the pedal while I crack the lines. As soon as the exiting air stops gurgling there, I quit, and;
Then I check for a high hard pedal.
If I don't get it, then I have to move on to the slaves. and then,
As soon as the pedal gets hard, and rests up against the stop, I quit bleeding.

As to which end first?
I always bleed the rear drums first, cuz they allow a longer stroke to purge the air which makes it go faster. Remember that you are pushing air downhill, and it's not always happy about that, so the longer strokes push the air further, and shortens the time for it to try and come back up hill.So you have a better chance of getting it down to below the floor line. Once down there, it's usually not a problem pushing it to the back; and once there, it's all uphill to the w/c's.
Theoretically, it shouldn't make a difference.
done.
 
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AJ/FormS said:
You loosen the M/C from it's mount, and withdraw it from the mount. This relaxes the pushrod, and allows the internal spring inside the M/C to push the piston back into the parked position, and that opens the C-port, and that allows the fluid to return, unlocking the brakes...
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A bit late, but I see this a lot. Why would one need to "relax the push-rod"? There should be nothing preventing the brake pedal from swinging freely as far as the MC piston wants to move it, i.e. no "unbolt from firewall" required. If the pedal is bottoming out on the brake lamp switch, that is wrong. Unbolt the switch until the brakes are installed, then adjust the switch to sense, but not affect, motion of the brake pedal.
 
pushrod is too long. The Spring DOES move the pedal as far as it can, but if the pushrod is too long the C-port does not open and so pressure remains in the system, dragging the brakes. Unbolting or just loosening the M/C allows the too-long pushrod to move all the back which opens the port and relaxes the pressure, releasing the brakes. This is the proof-test for a too-long pushrod, or a brake pedal not parking properly.
 
Sorry, just saw this. Still makes no sense. How can the brake rod to the pedal be too long? What is keeping the pedal from just moving further out? It should swing freely. If it is bottoming out on the brake lamp switch that is wrong. People keep doing that and don't understand. It isn't rocket science. If the switch is at max adjustment and still stops the pedal, then the rod is too long. Of course, you also would like the pedal to sit at a certain height, like same place as the throttle pedal.
 
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In 2012 I wanted to eliminate the power brakes in my '70 Charger. I tried 3 master cylinders that I had here, all 3 had different bore sizes: 1 1/8", 1 1/32" and a 15/16". ALL three gave the same results...firm pedal, minimal travel and brakes that were ineffective. I could barely skid the tires on gravel! The best was the 15/16" unit but it was still not great. I called and asked about a new aluminum 15/16" MC. It was no better than the iron one I had of the same size. I am not trying to talk trash on the sales guy but sometimes vendors are too fast to sell you something rather than to learn if their product will solve your problem. The $90 I spent made no difference and wasted my time.

When you deviate from a balanced stock setup, things can get screwy pretty fast. Several details factor into a well functioning brake system. The factory always made the front wheel cylinders or calipers larger than the rear. They had proportioning valves in a disc/drum system in the effort to have balanced braking. There are other factors such as pedal ratio, power VS non power and even the material used in pads and shoes.

4 wheel drum systems need NO proportioning valve. The front to rear brake proportioning is controlled by using smaller brake cylinders in the rear. The very same principal is in play with a 4 wheel DISC setup. The rear caliper BORE size must be smaller than the front.
 
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