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Dimples
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The '65/'66 cars did not have different pedals for manual and power brakes. For power brake cars there was an adapter that went between the firewall and the booster that changed the ratio of the pedal for power brakes. You can see it in the photos of this kit.
While true, many swaps for that application (65-66 dual res master w/booster) do relocate the pin.
 

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Discussion Starter #22
So I need the adapter and also need to relocate the pin too ?
I'm thinking what ever kit I got probably had the adapter with it as most of the kits I see online have the adapter included.
 

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We'll know more if you clear up what booster you have. Of course, the booster is not capable of improving braking. Boosters effect only pedal effort, not stopping. Of course, a malfunctioning booster can make things worse.

The OP keeps referring to lack of ability to lock the brakes. The ability to do this was standard equipment. The 200 I6-equipped Mustang, with 9" manual drum brakes, was capable of locking the wheels.

This means his brakes have a serious problem.
 

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Discussion Starter #25
Thanks to everyone for all the great information!
I will try to find out more info tomorrow.
it's one of those thing where I don't want to tell my mechanic how to do his job when he is the "expert"
 

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I've heard that the wrong pushrod for the booster can tear the diaphragm in the booster causing failure immediately.
 

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Discussion Starter #27
good info, but I don't think its a booster problem. It's a lack of pressure at the wheels that won't allow the brakes to lock up. So I'm leaning more to a m/c problem or the shaft between the booster and m/c.
Mechanic is supposed to be checking the pressures at the wheels today...
That should revile a lot.
 

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good info, but I don't think its a booster problem. It's a lack of pressure at the wheels that won't allow the brakes to lock up. So I'm leaning more to a m/c problem or the shaft between the booster and m/c.
Mechanic is supposed to be checking the pressures at the wheels today...
That should revile a lot.
ya it will reveal there's not enough pressure in the system which you already know since you can't lock up the brakes. Pushrod travel seems most likely or rear brake adjustment or air or some combination of 3 of those would be my guess. or bad MC but i think you said it's new.

Not to be a dick but I hope you're not paying much for that mechanic...
 

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Discussion Starter #31
ok so this is the kit I have:
mechanic added a bushing at the pedal pin to help with travel and seems much better.
However still can't lockem up
Interesting that both reservoirs are the same size, most seem to have a smaller front reservoir.
 

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ok so this is the kit I have:
mechanic added a bushing at the pedal pin to help with travel and seems much better.
However still can't lockem up
Interesting that both reservoirs are the same size, most seem to have a smaller front reservoir.
That kit has the adapter that changes the pedal ratio. The video says it needs 18" of vacuum at idle to operate the booster. Does your engine make 18" of vacuum at idle?
The reservoir size has absolutely nothing to do with stopping power. The size of the piston has everything to do with stopping power and the specs say it has a 1" piston.
When you try to lock up the wheels are you standing on the pedal with everything you have or are you expecting the booster to do all of the work for you? Maybe your engine is not making enough vacuum for the booster to do it's job efficiently and you need to apply more leg effort.
 

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Discussion Starter #34
Good point , and you may be right about the leg effort.
I haven't driven an old car on a few years !
@ BlakeTX I see we have the same manufacturer but a different kit
Wonder what the differences are as far as performance and application ?
 

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Mechanic is supposed to be checking the pressures at the wheels today...
Did he measure? Facts will make it way easier to narrow down the problem. Do the booster work? It's usually easy tested by pushing the pedal down before starting the engine. If the brake pedal lowers under the foot when the engine starts, then the booster is helping. If it's one of those kits that don't change the pedal ratio, then you will have a longer pedal travel than you are used to from modern cars.
 

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Dimples
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@ BlakeTX I see we have the same manufacturer but a different kit
Wonder what the differences are as far as performance and application ?
I"m confused. You have linked the Master Power brake kit, while I have the Mustang Steve power brake kit. Everything in my setup, aside from some modifications to the pedal and support is a Ford part (booster and master).

I'm not familiar with the Master Power kit, and I must say, I've never seen a master cylinder that is supposed to work with all drum, all disc, or front disc/rear drum. That's a new one for me.
 

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Forgot to mention: If there is any chance at all, as awhtx is saying, that maybe you're just not stomping on it hard enough, that would be my first test. Take it out somewhere where you have room, and stand on that pedal like your life depends on it. If you still can't get it to lock up, then we can keep trying to diagnose.

As a potentially separate issue, the suggestions about vacuum are solid too. But again, that's about pedal effort, not stopping power. Even if you disconnect the vacuum hose from the booster, your brakes should still perform, just with more effort.
 

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I've never seen a master cylinder that is supposed to work with all drum, all disc, or front disc/rear drum. That's a new one for me.
As far as I know a Master Cylinder is a Master Cylinder is a Master Cylinder, and on and on. The MC couldn't care less what type of brakes are being used at the end of the line. What makes a MC disc or drum specific is the addition of residual pressure valves built into the ports. So with the Master Power kit that the OP has you must install in-line residual pressure valves and a proportioning valve if you're using disc/drum brakes. 4 wheel disc or 4 wheel drum don't need a proportioning valve. I have neither RPVs nor a PV in my Granada/Explorer 4 wheel disc system and it works just fine.
 
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