Good Initial Timing and Too much Total Timing Problem. Seeking guidance to minimize total timing. 1969 Swinger 340 4 Gear

Dana67Dart said

I picked up my first antique dial back (snap on) light. I measured the total and it was about 61 with the VA can attached at some about 2000 to 3000 rpm.

It is a CAP dual point dist. And set at 5 before, spec is 5 after so it is 10 advanced over spec. That would have had it at 51 total with vacuume advance.

Engine runs as good as it can, 170,000 miles on last rebuild.

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Around 51 is typical for a smallblock (LA) cruising at high speed. Its in the FSM and its on the 1980s and early DC/MP instructions. I've posted those in the How To section. B/RB typically a little more - again listed on the instructions from ma mopar.
The OP has found that his combination is too much under certain conditions. The next step is to measure and plot out the timing and see what the combination is at the rpms where the pinging occurs.