Big Block Chevy w/ standard cam height; For external, dry timing-belt, cam drive systemsCam Sync Kit w Bracket 36 1 Tooth Crank Trigger System for Big Block Chevy Overview Holley's EFI Crank Trigger Kit is engineered to provide an accurate crank speed position signal to Holley EFI systems in the most demanding, high horsepower, racing applications. Crank position is measured every 10 degrees as opposed to every 45 degrees for a standard 4 Magnet, MSD "style" Crank trigger. It is designed for use on early model BBC Chevy applications