Hello Mr. Tom
I have run some motors on woodgas that were old enough there were no computers. 84 ford 460 V-8 , 87 dokota 3.9 V-6 and a 4 cylinder tractor . All of these I could retard and advance the time by a little twist of the distributor. In the case with these motors it made little difference in performance and speed and you would really have to listen or feel for it.
With the computerized V-8 dokotas and rams it is like night and day when the time is advanced. ( just ask anyone that has operated one 
) Little power and plenty of backfires if not advanced 
The experts say the timing can not be advanced on these motors. I agree but we can make them cross fire ( jump to the next peg or plug wire )
Below may be the thread you were looking for. Please try to stay warm.