1998 GMC Suburban Valve Timing

The valve timing is controled through the camshaft. Your timing chain may have jumped time butyou can check that by bring #1 up to tdc then see where you rotor is pointed. If it's pointed to #1 then it' s ok. But the proper way to adjust the valves on a small block or a big block is to bring the rocker down to zero then tighten the rocker bolt 3/4 to 1 turn unless you have the nuts s that are just torqued. They were either way on the later small blocks. The torqued nuts will be small and the adjustables will be larger nuts. Next time please pujt down engine size as it makes a difference.