1966 Mustang Brake Issues

ReturnToHanger

New Member
Feb 13, 2020
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I have a 1966 Mustang with a newly installed dual master cylinder with power booster. The car has front disc back drums setup. Also have the proportioning valve with built in residual valve for rear drum brakes.

Everything is plumbed in, but I am suffering from barely any braking power even with the pedal fully depressed. We didn’t have any brakes whatsoever even using the piston adapter, so we tested placing a nut in the cylinder with the piston adapter and got more brakes but still not enough. We have bled all wheels and bench bled the MC.

Please help. Maybe it’s a pedal pushrod adjustment issue?
 
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wicked93gs

10 Year Member
Sep 30, 2006
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Nashville TN
No one is ever happy with power brake conversions in vintage mustangs, they don't add any stopping power, they just reduce pedal effort. What is the brake line situation? Factory lines? Custom? Any of them running above the level of the master cylinder?(Made that mistake once). When doing anything custom on brake systems, I will always install speed bleeders...they are a big help. What size master cylinder do you have?
 

Woody3882

Member
Jun 19, 2018
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Bradenton Fl 34212
Last year I installed disc brakes on the front of my 65 Mustang. I tried many of the recommended applications along with the regulating valve in the rear drum brake line to balance the stopping. After numerous tries I came to the conclusion that pretty good is the best you are going to get (75%). The stopping power is adequate. Regardless of the position of the regulating valve the brakes still suck, but that is the best they can do without putting discs on the rear. keep your expectations reasonable. Every time I drive the car I flash back to how inadequate the old braking systems really were compared to modern tech.
Best of luck
Woody
 

PaulC69Convt

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Apr 1, 2020
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hi everyone,
with a conversion front disk kit with a power booster and 1"bore dual reservoir mc, shouldn't I be able to lock either the front or rear wheels? I still can't. I bench bled the mc and then the 4 wheels. new rotors & pads. any thoughts?
 

wicked93gs

10 Year Member
Sep 30, 2006
802
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Nashville TN
In all honesty, it sounds like a throw issue(which could well be pushrod). Personally I would use a 1" bore for a manual 4 wheel disc setup...but if I were to install a booster as well, I would be looking for a larger bore MC in order to take advantage of that booster and reduce pedal travel
 
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rbohm

SN Certified Technician
Apr 12, 2002
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i think the problem is the lack of a proper pedal ratio for the power brake booster. for the 65-66 cars ford used an adapter like this one for installing power brakes;


as you can see the pedal ratio is changed to allow for the different pedal throw with the power brake booster. in 67 ford went to a power brake specific pedal with a different pin location as opposed to the manual brake pin location. mustang steve has a number of power brake conversion kits for the early cars, one of which allows you to change the pedal ratio. check out this link;


more specifically this one is what you would be looking for;

 
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