Tuning For Detonation
Picture time
If we look at the timing spec's for a stock 225 they look like this.
If your engine has high overlap and other factors that reduce efficiency at idle, that's fine. The point here is to look at the shape. We see from the graph that in the factory 225 combustion efficiency really picked up around 1900 rpm.
Then to any rpm on that timing curve add the matching vacuum advance.
If you (RRR) can identify whether the detonation is occuring when crowding deep (no vac advance) vs when not so deep(some vac advance) then you would know which one is more likely to resolve the problem.
With the mechanical advance, turning the spring perch for the long lopp spring will bring into to play at lower rpm.
With the vac advance add wahsers or turn the allen screw to move the vac advance timing to the right on the graph.
Picture time
If we look at the timing spec's for a stock 225 they look like this.
If your engine has high overlap and other factors that reduce efficiency at idle, that's fine. The point here is to look at the shape. We see from the graph that in the factory 225 combustion efficiency really picked up around 1900 rpm.
Then to any rpm on that timing curve add the matching vacuum advance.
If you (RRR) can identify whether the detonation is occuring when crowding deep (no vac advance) vs when not so deep(some vac advance) then you would know which one is more likely to resolve the problem.
With the mechanical advance, turning the spring perch for the long lopp spring will bring into to play at lower rpm.
With the vac advance add wahsers or turn the allen screw to move the vac advance timing to the right on the graph.
