My ignition timing is going crazy, very unstable

ok what octane fuel o you run? here in the states you can get to 10* on most motor's on 87...

for checking the timing you need to disconect the vacuum line from the carb to the distributor, but remember to plug it with a golf tee or something so you dont have a leak...

then set the timing around 8*, reset the idle, and re check timing...

now tighten down the bolt for the distributor, after it is snug try to turn the distributor... if it turns there is another bolt under the dizzy for more adjustment need to tighten it up...