Excessive Ignition Timing Advance Effects

[Mark Mason]

Scenario:	IC engine
		compression ratio = 8:1 
		fuel octane = 120 unleaded
		engine temp = 70 Deg C.
		ignition timing = 20 Deg. BTDC
		RPM = 1000
		
If I start increasing the ignition advance out to say 40 Deg. BTDC, what
engine parameter or by-product can I measure which will tell me which
Ignition setting gave me peak torque at the lowest combustion chamber
temperature other than actually measuring the two parameters?

Thanks in Advance.

Mark.