base timing keeps advancing by itself...

Pertronix collar is tight and wires are in correct order, have been using same unit for years. But the issue does seem to correspond to heat… maybe it is electrical somehow.

As far as distributor advance springs, they looked fine. One heavy, one light, working as advertised. I guess i can pull the distributor and send it to Ray to check it out.

So far leading theories:
1) pertronix unit failing with heat. It is a simple magnetic trigger, no ecu so i dont see how this could happen. Although i have noticed cap contacts fouling very quickly lately. Plugs spotless. 0.040” gap, pertronix coil. Air gap set to factory spec. Mag pickup is firmly attached to vac advance can with no slop.
2) weak advance springs. They look fine, and this doesnt make sense as to why the engine is 10degrees retarded cold, and advances as it heats up.
3) cam gear is loose. No clue what timing set the engine builder used. The only thing I could think of is that maybe they left out the Woodruff key and it was just the bolt holding the gear on? But still as others have mentioned wouldn’t the cam retard under load, not advance? Also, why would it return back when the engine cools off. Although this would explain the erratic timing mark at idle, only moving a a couple degrees but still it should be rock solid at idle, right?