Triumph Repair: Unleaded - Timing advance?, octane enhancer, triumph spitfire

Question
Hi can you please help - My dad has a Triumph Spitfire 1980 1500cc as currently running on unleaded plus lead substitute. Timming set as per book ie. for leaded fuel (10 degree BTDC) - does he need to change timming? (NB he has no access to internet - hence my being middle-man - so please excuse any technical mishaps - not very mechanical me - unlike dad)

many thanks

Rob

Answer
Hi Rob,
It is normally not necessary to change timing when adding an octane enhancer. However, to gain the benefit of an octane enhancer you may advance the timing slightly. The trick is to find out how far you can advance it without getting into detonation / preignition. It is not hard at the lower RPM range because of the tell tail pinging from the over advanced timing. But there is a deadly detonation at higher RPM that is not easily heard. Deadly to the engine that is. I am not an agent for MSD but they do have a knock sensor LED display unit for detecting detonation. With that unit you can advance to the point just below detonation (which is the advance limit and the max power/performance as far as ignition timing goes)
A rough method is to get the engine up to operating temp including oil temp and advance the timing until you get the "Pinging" on a quick throttle opening from a low RPM, then back off the timing until you can't get the pinging. then check the timing and they called that their upper limit. I agree that works for most street cars however, I know from my racing background that if the advance curve of the distributor was not a good curve to start with you could still get high RPM detonation and a destroyed engine and not hear the problem until it had done damage.
If on a hot day and/or hot engine you are getting pinging on acceleration from a low RPM now with correct timing then I agree with adding the octane enhancer but don't change timing.
If you are getting pinging (detonation) now you may want to check that you are not burning excess oil (oil has a very low octane rating)
Run a fresh air duct to the air filters (hot engine air promotes detonation)
Keep you carb adjusted a hair on the rich side.
Use low temp thermostat.
Use Propylene Glycol in place of standard antifreeze.
Sorry, there is not a simple answer to you question.
Show this response to him as it may be of some help.
I hope this helps,
Howard