Front disc brake conversion questions.

[samert111]

I'm looking at the CPP front disc conversion kit 6370SWBK-6OE-S from Summit for my 68 C10 with power drum brakes with the dual reservoir MC that has equal sized reservoirs.

After talking to Summit sales support about MC and proportioning valve (PV) needed for the conversion, I was told I only needed to change the PV and my current MC would work. Well, every front disc dual reservoir MC I've seen, the front disc side is larger to hold more fluid. When I questioned this, he said it would be fine.

In the Summit Q&A section for this kit I've read that these are all basically 71 to 75 C10 components. So. I went to the RockAuto site and looked up a MC for a 71 C10 and they all have the larger front reservoir for the front disc brakes.

My question to you folks is, those you that have done this conversion were you able use your original MC or replaced it with one with the larger front reservoir for the front disc brakes?

Secondly, the PV recommended has the extra outlet port to run a separate line to each front wheel. Again, in the FAQ's I've read that some have just blocked off one of the front outlet ports and kept the single line to the original tee then splitting off to each side. Anyone done it this way or is it best to run 2 separate lines?

Lastly, has anyone installed this kit and could you tell me the dimension from spindle centerline to outer edge of caliper for wheel clearance. I have aftermarket 15" wheels and would like to know if the caliper will clear the wheel ID.

[1970cstblazer]

Not all '71-'72's used a reservoir that had unequal sizes front to back.

This one was used on a majority of '71-'72 trucks/Blazers/Suburbans..

[PbFut]

The different size reservoir is to accommodate the difference in fluid needed to fill the caliper bore vs drum piston bore as the pads and shoes ware down. The MC reservoir size does not effect the pressure going to the brakes. Hence non-issue relative to stopping performance and why summit answered as they did.
The correct proportioning valve is very important. It is what provides the correct pressures front to rear. Given you have different piston bore sizes, different brake types and different weight and transfer weight front to rear, the PV is the device that modulates the level of braking at each end. Too much at the front and it may feel like the rear becomes unstable under hard braking. Too little in front and rear will lock up and you feel little braking as most braking is done with the front due to weight, be it actual or transferred. If you change brake components, unless you use a complete kit designed specificly for the application to be installed on, then an adjustable proportioning value is the only way to get the system correctly balance.

[kwmech]

I think the difference back then was whether or not the system was Bendix or Delco Moraine.....if I recall correctly. I slightly remember something to that effect.

[michael bustamante]

just be secure in your mind and use the m/c for the disk/ drum system... calipers use more fluiid than drum brakes...
almost all 15" after market wheels will clear the calipers unless theyre from the 60`s

[LS short box]

On my disc conversions I run one line to a tee that I mount in the middle of the cross member and then single lines to each front brake. In the rear I do the same thing.
All my disc conversions have been discs front and rear. I use an adjustable prop valve.

[samert111]

Thanks all for the replies.

I think I'll give the CPP folks a call and see what they recommend.

[425HP409]

You have to use a master cylinder that is built for either all drum, disc-drum, or all disc. The outlet of the master cylinder for drum brakes has a check valve behind the tube seat for the line. This is to hold a little residual pressure in the drum system as the shoes are not in contact with the drums and keeps the wheel cylinder cups sealed against the wheel cylinder and helps the brakes apply quicker when needed. The discs do not need, and should never have this check valve or you will have residual pressure applying the pads to the rotors at all times.
Back in the day when we rebuilt master cylinders, the kits came with new check valves and seats which were replaced.