if your total initial plus mechanical is 30...then regular driving with vacuum advance would probably be 47 - 49 or whatever and all would be well...but at wide open throttle it drops back to 30 total.Would this cause harm or over heat your engine?
No, just a bit of performance and fuel economy loss.
Remember that for emissions the timing was set by the factory lower than that, until the RPM's got high enough to bring in all the mechanical.
I run my Magnum at 20 initial, add 14 with mechanical all in at 2,500 and a grand total of about 50-52 with vac advance under light throttle.
9:1 compression and I run 87 fuel with no problems.
