Couple of points I thought of while reading the posts above. Setting the distributor advance 9 degrees and getting 16 mechanical. You were pretty darn close, remember the distributor shaft turns at 1/2 the crank shaft. 9 degrees of the distributor is 18 degrees crank.
A camshaft can affect the dynamic compression ratio and thus cylinder pressure, by when it causes the intake valve to close. Compression of the fuel/air charge in the cylinders will not start until the intake valve closes. An engine with a 10:1 static compression ratio.can have a high dynamic C/R with one camshaft and a low dynamic C/R with another camshaft.
Maybe your camshaft was put in advanced, that would cause the intake valve to close earlier which in turn will raise the cylinder pressure. It's cylinder pressure that causes detonation, if one fires the plugs too soon or has a camshaft that closes the intake valve too soon, or has too high a compression ratio, the pressure will build higher than the octane rating of the gasoline can handle and PING.
16 degrees mechanical advance isn't that much, I think 20 degrees is about normal. I would want the advance all in at about 3,000 to 3,200 rpm. Set the initial to get a smooth idle and easy start, don't worry what the numbers are. Then check what your mechanical is with a dial back timing light or use the aforementioned timing tape. Try driving your car in second gear and give it a WOT run, if you have no detonation advance the timing two degrees, keep going until you get pinging then back it off two degrees. That is the total timing you want. If that results in an initial timing that is two low or too high to idle or hard starting adjust your timing curve to keep the total at the required number but increase or decrease the initial to something that works. If you are getting the detonation to stop at say 26 degrees total but your initial is then down at say 5, plug your vacuum advance to manifold vacuum, that will give you more advance at idle and keep the 26 that works for total.
I'n not an expert but that worked for me while trying to solve my detonation problem.
Thanks for all the detail. That is sort of what I have been doing. I keep retarding the timing to were I am currently at, total is 22 Initial 6 and mechanical 16 from here it still pings slightly. If I do hook up the vacuum advance on manifold, would the vacuum advance be active with part throttle? It should drop under wot which would pull the timing back down. Sounds like it would work. I'll give that a shot. I will try lowering a couple more degrees and see what happens.
