Advance and retard

[sparkplug]

Hi.
      I'm building a scaled up version of the four cylinder horizontally opposed Mastiff four stroke.    I've got to the stage of machining the contact breaker casing, which I've made rectangular to accommodate a set  of motorcycle points, rather than the normal round style.     I need to fit a quadrent to the base, to facilitate advance and retard.    Any ideas as to the amount of angular movement that might be required?
                Thanks. 

[gbritnell]

The average range for ignition advance is between 10-30 degrees. That's not saying that all engines require this amount of advance. There will always be an initial advance set and then you would go from there. With points operated from the camshaft, as most are, you would only need 1/2 of the required amount of the crank rotation so 10 degrees should be fine.
gbritnell