A cam sync signal is required to run sequential fuel injection. This tells the ECU which cylinder is cylinder #1 (or the first cylinder in the firing order as entered in the software). 

•Fits Big Block Chevy Engines w/jesel and similar external, dry timing-belt, cam drive systems

•Designed to provide a plug-&-play cam position signal to Holley EFI systems; Also compatible with any EFI system which can read a digital, square-wave cam input signal

•Bracket assembly can be mounted in up to five locations to accommodate various cam-drive systems and front accessory drive configurations