Factory disc question for those with stock disc brakes. NOT aftermarkets
I just finished putting '76 Scamp front disks on my 63 dart and a 75 dart rearend with the 10X2.5" shoes. I told doctor diff my setup (essentially a factory disc brake car) and he recommended the proportioning valve I would need. I purchased a new dual master reservoir listed for a 76 scamp with disc front brakes. Everything is in, bench bled, and bled with no more air coming out. I am currently running manual, no booster.
The brakes do not toss me into the windshield as I expected. The pedal is a little spongy, with quite a bot of travel. They sem to stop OK, but the pedal is not hard. It pretty much feels like the 9" drum system I replaced them for. The only thing I did (due to a rounded off line nut) is that my proportining valve front circuit is connected through one front port to the factory distribution block, rather than the two front circuits being connected directly to the proportioning valve. I also understand that the master listed for disc brake fronts may very well NOT be that, as I purchased it from RockAuto.
For those of you driving factory manual disc A-bodies from the seventies, what do the brakes feel like? Has anyone experienced this before? I specifically chose factory components to avoid the all-to-common disappointment of aftermarket conversions.
AS to your question;
I run the KH 4-piston set-up on mine with 10x 2s on the back, and braided lines on the front,
and with the Combination valve shown in Post-21,
and with a 15/16ths Dual M/C,
and with an F-body booster.
and I gutted that P-valve section, for use with 295/50-15s.
My pedal is high and hard, and the Barracuda is, bar none, the best braking car that I have ever had.
My guess is threefold;
1) the rear shoes are NOT adjusted tight enough, or
2) the inter-chamber in the M/C still has air in it. That would be the circled-in-red section shown in Post-18.
That chamber having air in it, is sortof a common occurrance/complaint here on FABO. Bench-bleeding it, should have eliminated that.
3) one thing rarely talked about, is rust deposits in the rear brake line, that present as a restriction. When the fluid passes from the high pressure side of the restriction, to the lower pressure side, it sometimes forms bubbles..... which then collect on the low-pressure side, giving a spongy feeling. Left alone over time, they seem to resorb into the fluid. But the next time you stab the pedal, there they are again. When all else fails, I cut out the lowest part of the line, and try it again. Sometimes I have to replace the entire line. But, more often than not, it's the rear flex-line that is the problem.
FYI;
I like the 15/16th M/C for it's modulation ability with my combo of a High Cylinder-Pressure 367 and manual trans. The 15/16ths requires more pedal-travel to do the job, and my left leg is used to clutching, which also takes a lot of travel, and I do a fair amount of left-foot on-the-gas braking.