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?
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?
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
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?
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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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;
65-66 Mustang: DO-IT-YOURSELF PARTS KIT (add $159 for Booster) Includes a new redesigned PEDAL PIN and the FIREWALL BRACKET plus the PLANS. This kit also works on 65-66 F-100 Ford Pickup with minor firewall modifications. Uses Fox Mustang 4-cylinder booster or 80 Fairmont booster, or...