Erratic Timing
Based on what you're experiencing, should be able to get the difference between in gear and out a lot closer.
Kickback is a good description - everyone gets the picture.
However kickback at over 10* is unusual with a hot cam. May be a fair amount of compression in the engine, and the cam although not stock, may not have much overlap.
You may be able to get better idle quality (ie. power) with 8* than 10*. The more power it has at idle, the less the rpms will drop when put in gear.
Also try an 1/8 and 1/4 turn richer on each of mixture screws.
But so as not to leave you totally hanging - In my experience, the critical area to get mechanical timing correct to work with vacuum advance is 1800 to 2800 rpm. That's when the car is cruising along for 45 minutes and you give it a little more throttle for a slight uphill and it starts to ping. :(
Great progress!
Based on what you're experiencing, should be able to get the difference between in gear and out a lot closer.
I don't think its technically detonation since there is no flame burning.
However kickback at over 10* is unusual with a hot cam. May be a fair amount of compression in the engine, and the cam although not stock, may not have much overlap.
You may be able to get better idle quality (ie. power) with 8* than 10*. The more power it has at idle, the less the rpms will drop when put in gear.
Also try an 1/8 and 1/4 turn richer on each of mixture screws.
Lets come back to that.