I found this on some summits web site under the product description for the residual valves. the master cylinderis mounted above the horizontal plane so do I need a 2 lb or 10 lb?
Ideal for drag racing, Street Rods, and many off-road applications, these inline residual pressure valves from Wilwood retain a minimum brake line pressure to help eliminate excessive pedal travel. These 2 lb. valves are used in disc brake applications where the master cylinder is mounted below the horizontal plane of the calipers, and fluid drainback occurs, causing excessive brake drag. With drum brakes, 10 lb. valves are used to compensate for return spring tension in the drums. They're made from billet aluminum and are color-coded for easy identification.