1987 Chevy S-10 seting of ignition timeing

It depends on which 6 cyl inder you have. If it's a 4.3L the you disconnect the tan with black stripe wire by the distributor and the timing is 0@idle. If it's a 2.8L then there is a taped area on the wiring harness beneath the heater in the passenger compartment. It is also tan with a black stripe and must be set at 10@idle. Next time put down what size engine as well as 6 or whatever it is as there were many variations of engines.