In conclusion I will follow the guide in bold :
11. With a tank full of Premium fuel drive the car uphill and try to accelerate with out changing down. Do you hear pinging (pinking) (a tinkling or small rattling sound) that disappears when you decelerate or change down.
— If so, try retarding the engine until the pinging no longer occurs. If it is evident that retarding the engine is futile, the pinging persisting but the engine losing power, then you need to use an octane booster, you local Premium fuel not having sufficient antiknock qualities. See Fuel. Remember that pinging is an extremely harmful phenomenon and every effort should be taken to avoid it.
— If there is no pinging gradually advance the timing until it can just be perceived, then back it off until the effect disappears.
This method of timing, although not text book, results in the best timing for your car with your fuel, without damaging knock or ping.
Hi Brit - yes, I've seen these instructions before. You are correct in your assumption - loosen the pinch bolt at the base of the distributor until it can be rotated, move clockwise by a small amount (3° is the angle for going from 98 RON to 95 RON, so that should be enough), lock it off and try the ping test under load as described.
I forgot to mention before, there are a couple of other causes of pinging - extra-sooty combustion chambers can lead to overheating in the cylinders (unlikely as your engine has been recently rebuilt and probably de-coked at the time), and high temperatures that might occur during the running-in period. I don't think either apply here, but as others have said, the quality of your fuel could be an issue. By adjusting your timing to suit the fuel you are using, you can prevent any long term damage to the pistons from pre-ignition.
PS - the rotor arm is the rotating plastic contact inside the distributor cap. The cap is held in place with two spring clips. The plastic cap is fragile, be careful when levering off the clips.
Mave - pre-ignition can melt a hole straight through a piston, and detonation (it does exactly what is says on the tin) is so violent it can shatter pistons in the bore. This is why EFI cars have a "knock" sensor - it is an accoustic transducer that monitors the shock waves resonating through the engine block when detonation occurs. When the ECU detects the condition it immediately
retards the ignition timing to stop any damage occurring.