Manual disc/drum brakes issues on hemi cuda, help!

hey folks, i am just finishing up my resto on our '70 cuda convertible, upgraded with a recent eddie haines built 426 hemi. anyway, i ditched the powerbrakes for obvious reasons. i kept the ssbc front discs and calipers, rebuilt the drum rears, installed a 1" bore master cylinder, and still have the proportioning valve to the rears from ssbc. i have a solid pedal after bleeding the system, but MAN, standing on that pedal barely slows her down. even the rears would not lock up no matter what the setting on the prop valve. pedal ratio appears to be 6to1. i am at a loss for ideas here, i have done a TON of internet searches, as well on here, i see a lot of people with my setup (or close to) doing just fine. any ideas? only variable is i am not sure of the caliper pistons/area.(ssbc 4 pistons). any, and all advice welcome, would love to get this baby on the street!

thanks folks,
davey

here is a link to the fire up:
http://www.youtube.com/watch?v=yGhFH91HIQo&feature=youtu.be

This is a common problem. Because SSBC uses small bore calipers, a 15/16" bore master cylinder will help.

thank you!
what would you suggest, new calipers with my 1" bore master or a new master with a smaller bore and keep the calipers? i want the best brakes possible, is there a 7/8" bore for mopar? so far, i am having trouble locating one, i kind of want it to look period correct, ie, no plastic if possible. i also have an adapter to go from four bolt to two bolt as far as masters go.

thanks again for the help doc!

davey

I stock 7/8" and 15/16" bore aluminum master cylinders.

'73-'75 A-bodies with power disc brakes used a 4-bolt iron 15/16" bore master.

I would also look into EBC "yellowstuff" brake pads. I think SSBC uses a late '60s Mustang spec (4-piston) front caliper.

thanks again doc, so the power master from the a-body's will still work with my manual linkage? it has the depth in the piston to hold the rod? unlike most power mc's i have seen that are shallow? (mopars are newer to me, mostly a pontiac guy)

i measured line pressure last night at the front calipers, 700psi under what i felt was 'normal' foot pressure, (no pedal gauge for lbs applied), and what i would call a 'panic stop' was about 1200psi.

i took the pads out, roughed them up on a flat surface, and scuffed the rotors (spinning them with a drill and lightly deglazing them with emery cloth) and it seemed to help. so, maybe the 15/16ths master and some yellow pads might get me there you think?

thank you so much for the help, i really appreciate it......

davey

Yes, every 15/16" bore A-body master I have seen has the receiver groove machined into the back of the piston.

I know you don't want to hear this, but this is a very common problem when using a brake kit that is made up of generic parts. People buy the generic brake kits because they are cheap, but if they don't work, cheap isn't a good price.

DoctorDiff sells Mopar brake kits that work. You're lucky that he is kind enough to jump on here and help you solve a problem with a kit that isn't even his.

Quote:

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You're lucky that he is kind enough to jump on here and help you solve a problem with a kit that isn't even his.

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@ andy, i am well aware this is not his problem, nor is he obligated to help me. i bought the car with this kit on it, and i am just doing the gearhead thing and working out the bugs so my car works. if i would have started from scratch myself, i would of course sought an expert such as himself. i have also thanked him at least twice in every post, and will continue to thank everyone here who is kind enough to help a new mopar brother out. i would hope 'luck' isn't a deciding factor on people chiming in to help others on here, maybe i should have been more specific in my first post. but, thank you for reminding me to always say please and thank you.
and on that note, thanks doc, i will decide what to do next now that i have some info at hand......


davey