1 - Get the timing to the max initial the engine will live with, sometimes it takes a recurve to manage total. I would expect you need at least the 16 initial you have, but if you can go to 18 it may fix it, but be sure to know your total, would hate to hurt the engine. I'd think you would want a max of 36 total with the compression you run
2 - Once timing is set, adjust idle air/fuel for best idle and lower the idle as much as it will live with (doesn't have to be excessive) A tipper here is if your ported vacuum port is alive at idle. If it is, then your throttle plates are too far open. Don't be afraid to take your time. Adjust a/f, lower idle, readjust, lower idle a little, it doesn't take a lot
3 - Make sure the engine is running cool, 195 thermostat should be OK, but if the car is overheating, you'll continue to fight it and fix that first. Sometimes the engine needs more fan, especially when it's fresh, see below.
4 - Get some miles on it and readjust the carb. A fresh motor makes heat from friction, that hurts in two ways, the heat can cause run on, but also it requires the engine to need more throttle plate opening to keep the motor running. As they loosen up often you can turn the idle setting down a bit
5 - Last as a band-aid you can run manifold vacuum to the advance and readjust the idle, it will add advance at idle and drop out when you hammer it, but I don't like doing that, I can never get the consistent idle I like, lots of guys love it though. You shouldn't need it though, as I think Bill said, 2 degrees and a good carb adjustment should get you there
In the end, your goal is to close the carburetor plates more, you can do that by adding a little timing and adjusting the carb a/f
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 445 cid FE, headers, RPM intake, 1000 HP series Holley, 4 speed