Well said Thomas, and now maybe I should admit I was wrong to doubt everyone.
I have established one fact that I find interesting: with my engine definitely set on perfect static timing of 10 degrees, I made a mark in white paint 25mm forward on the pulley from the TDC mark and did the strobe thing. I was surprised to find that in order to get this maximum advance set correctly I had to retard the ignition quite a lot, ie. turn the distributor clockwise.
This made the tickover less smooth....nearly stalling, but I soon sorted that out.
So I may need to go on a long journey this week to be sure what difference that made. It sounds good, maybe a little bit quieter.
So thanks for the advice to everyone and maybe I am now convinced that this strobe timing is important.
It's possible that there's a bit of wear in the centrifugal advance unit, weakened springs etc that may allow too much advance too soon.There's usually stops built in to the advance unit to limit max. advance. Iirc on Fiat bob (advance) weights there were little plastic buffers inserted into holes to prevent noise, maybe these are missing. They look like little pieces of black plastic pipe maybe 3?mm in diameter and the same thickness 3mm? as the bob weight.
I remember rebuilding Lucas distributors in Technical College. Used to run them on a proper Distributor Tester. It was possible to plot the advance curve. There were different springs available so the shape of the curve could be altered to suit different appilcations. In a previous post I mentioned that the two spring are usually different, the lighter spring controls the initial advance, then the heavier spring which incidentally has some free play built into it's mountings, then comes into action. The use of two springs gives an advance 'curve' instead of a linear advance. Some people think one spring is loose on it's mountings and tighten it. Wrong!
Iirc, the max. advance was marked on the advance unit base plate?
I think that too little ignition advance up to say 3000rpm makes the engine seem sluggish and too much advance can cause damage. The only indication you might get of excessive advance is 'pinking' a tinkling sound from the engine particularly accelerating from lowish speed in a highish gear. Iirc, this tinkling sound is the sound of the pistons crowns flexing.
If the engine seems to surge when cruising on a steady throttle opening, the ignition timing may be over-advanced also.
Be aware that most engines when timing is set 'by ear' to where the engine sounds 'happiest' or 'smoothest' are likely to be over-advanced. Which is why I originally said, find the smoothest point and then retard the ignition timing slightly. Then test drive and watch for the above pinking or surgeing.
Al.
