When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Doesn't have to be timing, but it's likely. things like carbon tracking in the distributor cap or plug wires shorting or bad vacuum leaks can do it also.
What you described will work. you should check it without the vacuum advance hooked up then after setting the timing hook it back up, preferably to ported vacuum.
I'd leave the hold down bolt loose enough you can move it while it's running, if it's still popping try adjusting it a little to see what makes it better or worse.
Well thank you to all that responded. I was 100% that the timing was on but that’s what I get for doing my own thinking. It was the timing I was setting it one tooth after ATD. I guess I will pay more attention to the marks I make next time and be a little more accurate and once again THANK YOU TO ALL FOR THE INSIGHT. Many helpful techniques!