Is the 4.3 v6 Chevy vortec engine a interface or non in regards to timing belt and valves?

The 4.3L Vortec V6 engine uses a timing chain, not a timing belt. Therefore, it's considered non-interference. This means that if the timing chain were to fail, the valves and pistons are less likely to collide and cause catastrophic damage. However, while less likely, damage is still possible depending on the nature of the failure.