Richard,the dampers on my truck are all marked for degrees,I set my made timing pointer on 34 degrees with the engine on compression, ya know both valves closed,turn rotor to fully advanced by hand and check to see if the points are just opening, like a few thousands.You can check with a home made buzzer or light, a piece of cellephane between the point contacts that just gets loose or whatever.But it's been my experience by checking with a timing light afterwards,I'm always with a degree by using the eyeball.The 32- 34 total degrees figure on 235-261 engine comes from personal experience and the advice of others. The vacuum advance is not an issue when doing static timing with the engine stationary, the normal no vaccum position is correct. On the 261 in my 37,the initial adavce is around 14 degrees with the modified distributer so the mechanical advance adds about 20 degrees to that at 2800 rpm.My Brit bikes have no timing marks at all,I use a timing stick to locate the piston distance below TDC that corresponds with the correct total degrees of advance, as in before TDC.In fact the magnetos have no advance system at all,you retard or advance the timing with a handlebar control.Retart it to start and push it to full advance for running,no problem.
On a stock engine, initial advance setting is adequate, but on any performance or modified engine, total mechanical advance is what you should be looking at.
