Series III 2.25l ignition timing riddle

[Arayat]

Here is one for true engine geeks What ignition timing is best for a 1982 LR with 2.25l engine (all original)? Ok, the label in the engine bay says: 6° ATDC at idle speed. I remember the manual said TDC and 6° ATDC for low octane fuel. On the internet I find three choices: TDC or 6° ATDC for engines with emission control and also 6° BTDC for 7:1 compression engines. Mine has no emission control, at least I can't see anything I could identify as emission control (by the way it's an Australian-made model). My mechanic says he normally sets it to 6° BTDC (for whatever reason). The engine definitely idles faster at some degrees before TDC. At 6°ATDC it runs not so well. Questions: Any reason to set the timing after TDC at all? How can an engine have best performance when the ignition misses the first 6 degrees of the working cycle? And does anyone know about this emission control thing and why it would require such a late ignition? In essence I want to know what timing is the best, and I can't believe that 6° ATDC as per the label is the final wisdom. Thanks for any well-founded advice. Marc

[Spike555]

This does not apply to a LR but on all the dizzy engines I've set timing on we always juts set it by ear.
Drive it until it is fully warmed up, set the timing.
Test drive, adjust as needed.
But usually just setting it at idle worked best.