Question on air/fuel mix screws

Techinspector or others what would cause these to not respond or very little response.
Let me tell you how this started.
383 with about 12:1 and I was not paying attention and put in 83 octane. Started to get ping and so just to get home I added octane boost and backed the timing off about 8 degrees so it would stop.
Now fuel is out I changed the plugs and reset the timing to 36 degrees at 2800 rpm
tried to adjust the screws and getting no response. Also big stumble off the line this might be another problem but did not have any issues before the low octane fuel and changing the timing

Passages pluged. Throttle plate opened to far.

Junk fuel strikes again, I'd say... Like Mikej said, probably have some gunk in the idle passages and other passages in the carb.. Doesn't take much to plug up the circuits in a carb. Might want to take the carb apart and use some carb cleaner and an air hose to blow all the passages out, reassemble the carb, replace the fuel filter, and see if the problem is cured...

I agree. Pull & clean the carb.

Thanks I will try it and see what happens