Timing a "unknown camed" engine....

Stiffer advance Springs will slow the curve.
Open chambers, flat tops with a cranking of 180 might like 2800-3000rpm full advance. The initial at 20 is ok, you could get higher but that would shorten the advance divide between intial and full, anything less than about 8 degrees advance and you may as well lock it out at 32 degrees and call it a day. If you get light pinging with 35 degrees total. ..you need to back it down or get better gas. If you meant it pings with vac advance hooked up, then scrap the vac advance because if you can't run much more than again about 8 degrees vac advance...its not worth it.