From another site:
''Its also worth noting that the best ignition timing in any given engine, is to achieve the most advance it can tolerate without pinking. ( Audible pre-ignition).
This is achieved by setting your V8 timing to about 4 deg. BTDC (assuming you've been through the distributor check list completely). Then tighten the distributor so that you can (with effort) still turn it by hand. ideally put a tip-ex mark or small scratch on the distributor body and engine block to record this spot.
Next road test the car and simulate high load by quickly shifting into a high gear or if Auto allow to change quickly up to 3rd or 4th Ideally you need to find a small hill or incline, now if you apply full throttle the engine should respond without pinking, find a safe place to pull over, open the bonnet and turn the distributor through a couple of degrees only, anticlockwise, this will add slightly more advance timing and if you do the same test, and repeat it until pinking is noticed you will be very close to your absolute best timing criteria
So now all you need to do is turn the distributor clockwise by the same amount by an amount to counteract the last adjust, retest for the absence of pinking and that the job done, you will have just achieved the best maximum timing position for your car''
Done by that method mine - 1986 Flapper 3.5 EFi - is at 6 deg BTDC according to the pointer & marks on the crank pulley. The LR factory manual says mine should be TDC+/-1deg.
Noticeably better at 6 & it's been at that since just after I bought it in 1994 so you're not going to do any harm.
