Chevy & GMC Vans

i was told it needs to be at zero.can i just put a light on it or does something need to be unplugged?thanks

You'll see a cylindrical, single wire plug near the distributor on a distributor wire. Unplug and set timing to 0*. It will set off the check engine light. After you are done, unplug the ECMB fuse for a bit to reset the computer.

thank you very much.

With the wire disconnected you can also advance the timing to +4 or 6*. The computer will not no you did this and your whole timing curve will be advanced,base +4 or 6*.I did this on my 95 5.7l engine.Should give you better performance and mileage.