The factory service manual states to loosen the rocker shafts before replacing the timing belt. I’ve always obeyed that but can we discuss why it’s necessary? Any thoughts, opinions? It adds so much more labor to the job.
When installing the timing belt, there will probably be times when the cam timing is not correct. By loosening the rocker shafts, the valves stay closed, and any possible valve/piston conflicts can be avoided.
With practice and good methodology, the cam timings should be near perfect throughout the process, but **** does happen.