I went to start my 68 with a mild 350 a week ago, and as usual it took some cranking (about 4, 5 sec. tries) during which it made an unusual noise as I turned the key to off. Not sure how to explain the noise almost as if it spun backwards or spun too fast, it had not fired yet though. After another try or two she fired up and went to a strong 2000 rpm idle, oddly since it is set at 900 rpm.
Later after a short drive with noticeably better performance than normal, I proceeded to adjust the idle screws out to lower the rpm and got it down to 1800 rpm. Also I tried to adjust the dist. clockwise, it did idle lower but ran terribly and smoked from exhaust and valve cover breathers. It is normally as far counter clockwise as can be due to carb and vac. advance locations. Friends asked about vacuum leaks or moisture in the dist., both check out fine.
I havent done anything to it since it ran last maybe 2 weeks prior and couldnt think of any factors to explain the idle speed change (ie weather, fuel, maint.). Could the timing chain have skipped a tooth, is the dist. at fault, am I missing something?? Any thoughts would be appreciated.:clonk:

Hmmm Increase at idle usually means a vacume leak somewhere. But the fact that you said it ran better makes me think an increase in timing adv. Becuase if it is a vacume leak, you would have been way too rich in your original tune for performace to increase with additional air from a leak. If the chain jumped a tooth it would run worse, if at all. Go through the tune. Check timing setting and curve. Check vacume adv can to make sure it works and has no leaks. You say you adjusted the idle screws out to lower rpm. Out is richer. I would think you would have adjusted the throttle setting to lower rpm. The more I think about this the more I think its carb. Verify your ignition first then go through the carb tune.
Bill

The idle set screws were what I adjusted outward to slow the idle, the screws on the throttle linkage. After a little quality garage time the vac. advance actuator is okay. Ill check more soon.