This is typically performed on a dynamometer – creep up on timing until performance stops increasing – for a starting point, use expert opinions – more is not better with timing. Cranking at “Distr Base Timing” is often OK at about 10 degrees and cannot be changed unless the distributor is also moved to re-sychronize. Idle can often be pretty good at 15-25 degrees (depends on the cam). 1100 and 45kPa can often be similar to the idle timing. Most engines need only ~15 at 1100 RPM WOT, and 29-36 degrees at WOT 3000 RPM. Cruising 45kPa will easily like more than that – 40+ degrees at 3000 RPM is common – but watch out that you’re not too far from the “Distr Base Timing” or there will be arcing under the distributor cap, which can sometimes cause surging if it misfires. The 6000 RPM settings can often just be the same or a little more than the 3000 RPM settings.