Front disc conversion on '65 Barracuda FS

Bob Jasinski said
OK, so I have spent hours going through the sticky writeup, and numerous other posts about front disc conversins on early A bodies, but I need some input on implementation. I have a full KH setup, and now that I have my car finally out of the body shop, it's coming together. All the lines will be new, and I contacted Inline Tube about what lines to order as well as fittings. Since I'm going with a dual pot master cylinder, they said I should order the BLK 241 distribution block https://www.inlinetube.com/collections/all/?q=blk241 , the ADJP01 adjustable proportioning valve Products, and the PAB6402 Products Line kit.

I have the Raybestos MS36406 dual pot master with 15/16" bore ordered from Rock Auto. Currently there are new rear wheel cylinders installed that are stock units, (Dorman W78734) that are 15/16" (.9375') diameter. Rear brake shoes and drums (10") are new by Wagner. I know many have used the factory style "Texas" shaped distribution block with built in prop valve (I have a used one) but do not like it for a few reasons. First, it doesn't fit very well in place of the old brass drum-drum block, I'd have to drill some new hole(s) in the frame, I don't want to install the warning light in my dash, and as far a I can tell, it is not adjustable.

I've read in a number of places it would be better to go with a smaller diameter rear wheel cyls of 13/16" to provide better balance with the front discs. I'm willing to change these new ones out (system is still dry) but is it really needed with the adjustable prop valve? If I did go with smaller rear wheel cyls, would that eliminate the need for the prop valve? This will be a manual disc/drum brake system, and the car will have modern radials, same size all around, close to factory diameter but on 15" Ralleye wheels. Input is appreciated.

Here's some current project photos:

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I upgraded my '64 Barracuda to KH 4 piston disc up front last spring with the same MC I believe you have. The rear is an 8 3/4" with 10"drum. I had issues with the rear locking up when I test drove. I read somewhere the same as you to put in smaller 13/16" rear W/C but once I got them in hand, I could see that they wouldn't fit the backing plate nor the brake shoes(pic) so I abandoned that. I broke down and added an adjustable proportioning valve after the newer style Combination valve in the rear line. Once the Adjustable was in place it immediately stopped the rear wheel lock up with out any adjusting. With a little stop testing and adjusting, the fronts do most of the work and the stop distances decreased dramatically and no lock up anymore.

Beautiful car BTW, I almost wish mine was a formula S but I am kind of fond of the P/B transmission and its uniqueness that only '64 had.

As stated before the factory parts may not work with change in tire size etc. I have 14" rally wheels (factory was 13"), SuperStock rear springs and 0.92" torsion bars. So not factory at all and with the higher spring rates can change the way the car handles.

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