Petrol engines 2.1 Timing
5 BTDC degrees for unleaded on a DJ and disconnect the vacuum advance and retard and block hoses to time.
HarryMann said.. Valve seats are hardened but CR is high at 10.5:1 so it's just a matter of Octane rating and pinking/detonation. Dropping the static advance back about 5 degrees will just reduce performance a bit, but engine will run fine!
If 98 is available then use that with the ignition timing at 10 degrees BTDC
If only 95 available you need to set the timing to 5 degrees BTDC (or damage the engine)
If there is only 91 unleaded, then you are in trouble.. I dont think the DJ will happily run on that even with timing set to 0 deg ....
DJ - Disconnect the two three pin plugs on idle stabiliser unit and join together
disconnect single wire for idle system (have seen it as two wire on late syncros)
Disconnect vacuums to disi and block the pipes, golf tees are good for this check idle is ok at 800rpm +/-50rpm, adjust on throttle body /afm if necessary and set timing at 5 degrees for unleaded, 10 degrees for Superplus and LPG
Haynes is correct for DJ just a bit windy written