I am converting my brakes on the elky from drum to 4 wheel disc, I have a 12 inch c3 rotor setup with 70s chevy pickup single piston calipers up front. On the rear i have 12 inch wilwood rotors with the same single piston chevy truck calipers as on the front. so in essence I have the exact same brakes front and rear. I will be using a 77 corvette master cylinder 1&1/8 piston and a summit adjustable proportioning valve on the rear line. Here's my question. The summit valve comes with adapters for 3/16 line. my rear braided flex line is also 3/16 [this is the line that replaces the stock rear rubber line] should I run 3/16 line the length of the frame or stay with 1/4" like the factory had?I am also using a hydroboost system and a line lock on the fronts. I hate running brake lines as I am allergic to dot 3 brake fluid so I really only want to do this once. thanks for any help with this.

If your flex line is 3/16" just run a single 3/16" line from the prop valve to the flex line. It's not worth the trouble adapting to 1/4" just to reduce it further. The least number of connections in the lines will be the less trouble.

On a related note, where did you get an axle flex line in 3/16"? Both disc/drum and drum/drum cars the line was 1/4"...

Use Synthetic DOT4. Prestone, I believe, makes it in a synthetic that can mix with DOT3. It also has a higher boil temp ceiling.