After disconnecting vacuum, I set my initial timing at 8 adv. 3000rpm takes me to 27 adv total. I drove it and it pings at WOT and under heavy acceleration.
I hooked up manifold vacuum, and have an idle timing of 32, and 52 at 3000rpm. It seems to idle better but driving it pings easily.
I read that manifold vacuum is necessary)(
http://rockridgefarm.com/vettdoc/Timing_101.pdf) "...you need vacuum advance, connected to full manifold vacuum. Absolutely. Positively."
But I've heard from others including that mechanic that you need ported. Also, here (
http://www.73-87.com/7387garage/drivetrain/hei.htm) gives tips on setting timing with an adjustable vacuum can.
I'm so confused!! What is right?!?