I have a 63 skylark that I'm converting from drum to disc brakes on the front. I have an adjustable proportioning valve for the rear brakes. The dual master cylinder I purchased has both reservoirs equally sized. Which port on the master cylinder is for front and which is for the rear? Since both reservoirs are equally sized does it really matter which port goes where? Keith
Generally the front port is for front brakes, rear for rear. I hadn't though about it before, but that "could" be reversible as long as the master cylinder reservoirs are the same, the MC valves and respective orifices in the MC are identical. But since we don't know about the inside stuff, my advice is to keep the front MC port for front brakes, and rear for rear. Please share more about your master cylinder choice, and the front disc upgrade too. I haven't dealt with drum-to-disc conversions in a long time. Usually the front discs require more fluid volume, thus a larger front reservoir compared to drum. As expected, four wheel disc often uses same size MC reservoirs, though larger in volume than four wheel drum. Devon
Generally, I have seen front be front and rear be rear. Is it a small master cylinder like a 4-wheel drum car comes with or a large one like a 68-70 A-body with front disc brakes comes with? If it is the larger, it may work well with front disc, rear drum and an adjustable prop valve. If it is the smaller, it is likely not going to provide the volume for the front disc. You can try it to see what happens but don't drive it until you test the front brakes. Small drum/drum master. Larger disc/drum or disc/disc.
I did a scarebird kit front disc brake upgrade. The rotors are late 80's Mitsubishi Galant. The calipers and pads are early to mid 80's chevy s10 4x4, not the 2wd ones. The hoses are 79 or so Cadillac hoses. The caddy hoses are 15" long and most others are 12" length. When I bought my kit many years ago scarebird recommended your choice of 2 different master cylinders. First recommendation was the late 60's AMC dual master cylinder. Second recommendation was the late 70's Ford Fairmont dual master cylinder. Now scarebird only recommends the Ford Fairmont master cylinder lol. I have one of the AMC master cylinders. If I remember correctly the AMC master cylinder has a 1" bore and the Ford Fairmont master cylinder has a 7/8" bore. Keith
The larger bore has more volume per stroke but higher pedal pressure if not power brakes. The smaller bore has more pressure so discs will not be as hard if manual.
Front disc brakes was not an option for the 61-63 Y body cars. There is very little aftermarket support for these cars. This type of setup has been used on a few of these cars. I wasn't going to pay upwards of $1200 for a conversion kit when I could do this for a fraction of that price. Keith
