The compressed fuel air mixture is ignited by a kernel of flame around the spark plug tip. The flame front expands outward toward the combustion chamber edges. Pressure is applied to the piston and it travels down the bore. The maximum combustion pressure should occur when the piston and connecting rod big end are in the optimum position. A pressure spike that occurs when the piston is too close to top dead center produces poor leverage on the crank. The big end bearing is too high in the cylinder stroke. Excessive combustion chamber pressure occurs and head gaskets blow, rod bearings get hammered, etc. Power is not optimum.
A pressure spike that occurs when the piston is too far down the bore happens when the crank pin is in a great position to provide leverage. Unfortunately, the piston is a ways down from the cylinder head and compression is low. The peak combustion pressure is low. Power is not at its best.
The peak combustion spike should occur exactly when the rod big end is far enough down to provide good leverage and the piston is high enough in the bore to provide a compressed mixture for combustion. Optimum power results. Two things can be adjusted to get everything working right at a given rpm, and these are fuel burn characteristics and ignition timing.
Some fuels have a large fraction of heavier hydrocarbons and other characteristics that make them burn slower with a less pronounced combustion pressure spike. These are "forgiving" and they will work with a wide range of ignition timing settings and combustion chamber shapes. Other fuels are fast burning and produce more pronounced combustion pressure spikes. These "flashy" fuels will produce more power. To do this, ignition timing needs to be correct.
The first step in this tuning is to get the exhaust and intake harmonics sorted and the mixture correct. A conservative ignition timing curve is used for this. The next step, in the old days, was to scribe marks on the points plate so it could be rotated at 2 degree increments in relation to crank position. The Triumph has a "black box" instead of contact breakers. Three are being sent to Dorset, in southern England, for for programming. The curves will be 2 degrees apart.
The peak torque is measured on the dyno with the conservative timing setting. The timing is advanced in 2 degree increments and the power increases, usually. There will be a few settings when it dose not change. Finally, at some far advanced setting, the power will drop. This work develops a timing vs power curve. The ignition curve that is selected produces a smidge under peak torque on the retarded side of the curve.
The timing setting done here should be OK for Gairdner. Both places are at similar altitudes. The same gasoline will be used for testing here and racing in AUS.