I had the same problem on my mustang, I changed to the disc disc master cylinder and it cured the spongy pedal. I used 85-86 SVO mustang part. The so called proportioning valve on the drum drum cars is more of a distribution block than a valve. I know most will no beleave it but, if you take it apart and look at it you will notice the front and rear hole diameters are the same. This web sight has a Q&A for brakes that is pretty good. http://www.mpbrakes.com/technical-support/reference-master-cylinders.cfm
That make sense. Never thought about it before. The front brakes are much larger than the rears and would have more stopping power. So you probably get like a 60/40 bias just from the shoe size with equal pressure in the lines.
Hey thack, i was considering running one of those svo master cylinders, but i wasnt sure about the push rod. were you able to just put the mav push rod in to the m/c? are you running power brakes with that m/c? What brakes are you using on the front and on the rear?
