Telstar 85/AR-timing issue

[Flokos]

Dear all,
My tuning seems to not match the specifications of the manual to ignition timing BTDC of 6 degrees. The car seems to have a loss of power while picking up speed or handling steep roads. While the stroboscope shows a jumpy market, I've noticed that if the setting becomes around 10 degrees, the engine has a bit more revs, and during driving, a lesser pedal depression seems to accellerate the car better and makes it handle steep roads easier with lesser revolutions loss. The gears pick-up is more smoother too.
As part of my oil leakage inspection, the timing belt was inspected and the camshaft markets match arrow to arrow and the crankshaft's marking does too.
Still at 237,000 kms, the car burns about 10 kms per litre for a city n' careful driving, but the 6 degrees setting arranged a few times in the past showed overall an increased petrol consumption, about 420-450 kms per 50-52 litres, and a bit lethargic engine.
Also, with the 6 degrees setting, the gear changes show a larger revolutions change, compared to a (say) 10 degrees setting.

I'm also concerned if I do damage the engine with the 10 degrees setting, ie, does this influence (better or worsen) the positioning of no.1 piston readying for petrol combustion and maximising thrust?
Do I go with the performance of the engine on the road, rather than the manual? If the 6 degrees setting is correct, something else may be wrong for the lack of responsiveness of the engine.
Note: the idle mix adj screw was adjusted by a mechanic many years ago and there is no protective plug. He then told us that when its screwed inwards and the engine seems to 'gasp' for air, at that instant, it must be rotated anticlockwise 1.5 turns. I have not touched this screw for years and due to other 'repairs and new damages' done by those (sorry) experts, I do not trust leaving it to them for further experiments.
I know that these are many questions but I feel that a few minor adjustments may correct these interconnecting issues - I'm still learing with the car and its mechanics as you can see. Thanks, Flokos

[smally289]

Don't stress too much, I reckon every AR / AS Telstar that I've ever tuned has had its timing set to 10 or 12 degrees advance. The symptoms you describe when set to 6 are the reason why.
Have a play with the mixture screw yourself, you can't hurt anything. If you are worried, take note of where it's set now, so you can always put it back where it was. Go for a drive and get the engine nice and warm. Leave it idling and slowly screw it in until the revs drop and the engine becomes rough, then slowly back it out to get it smooth. If you go too far out it will run rough again - just screw it back in a bit. With a bit of playing around you will find the right spot. Just make sure that the A/C, headlights etc are off and if the thermo fans kick in, wait for them to stop before you do the final adjustment.

[Flokos]

Thanks Smally351 for your support and response, quite surprised of the double-advance settings, I wonder why the specs detail otherwise... Flokos

[dirty hands]

the other possiblilty is the harmonic balancer
has slipped on its rubber ring