Demon rated their carbs by cam duration.

""A Speed Demon™ carburetor is ideal for muscle cars, stock rebuilds, tow trucks, mild performance applications and crate motors. They are designed for engines with cam profiles between 220 and 240 degrees duration at 0.050".""

""he Road Demon Jr promises to be the ideal carburetor for budget-conscious enthusiasts needing a carburetor for performance upgrades for stock to mild performance levels. Its designed for small block V8 engines with cam profiles from less than 220 degrees duration at 0.050".""