Popping sound in exhaust

dart_68 said

When it was popping it ran so bad that it wouldn't idle on its own. I had to keep blipping the throttle to keep it running. Once I pulled the Vcan it didn't pop any more and got it to run fairly smoothly. It was only then that I could get a good timing read.

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With the v-can attached to the intake port, you likely had 60+ degrees of advance.... no wonder it mis-fired. The throttle blipping reduced the intake vacuum level level for a moment, the total advance probably dropped to the 40's-50's range, and the engine would fire properly and smooth out for a second. If the v-can had been attached to ported vacuum, then you never would have had that amount of over-advance at idle.

Now it's time to reduce the advance and see if you can start tuning the carb settings.