Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
With only 16 deg BTDC, your timing chain is not wrong. It would be miles off. Are you sure you understand the different between ignition timing and valve timing? Your checking the ignition timing and that is adjustable. First jump the A B terminals of the ALDL connecter under the dash (see pic of connecter below) and then turn the distributor to set the timing to the spec on the label under the hood. I tried to look up a spec and the book referred me to the label.
I just recently purchased a 2004 Tahoe with 155000 miles