Do i need to unplug anything to set timing on 98 chevy 350?
The only way to set the timing is with a OBDII engine scanner. You CANNOT use a timing light. The timing is computor controlled.
It all depends on what year the truck is. If it is the older version with the round distributer cap, you need a timing light. Connect the timing light to the number 1 cylinder, which is the front one on the drivers side. next you have to put the computer in base timing mode. To do this you need to locate the timing connector, which is usually located in the passenger side under the carpet…
You can not use a timing light to set the timing on that year engine. The ignition timing is COMPUTER CONTROLLED. If you have not fooled with the distributor then there is no reason to adjust it. But if you have bother it then you will need an oBDII engine scanner to put the timing back to factory specs.