Sayfoo

General question here.
As engine speed increases from idle (no load, in neutral), does the engine smooth out, or does it just seem so because of the higher rpm's.
My more or less stock 69 BB does not idle smoothly at all, and still runs rough up to about 2k rpm in neutral, where it significantly runs smoother. Normal or ?? Don't notice any significant off idle roughness while driving.

illenema

Might be running Rich on idle mixture. At about 2k the carb switches over the the main jets and no longer relies on idle mixture to run?
Lean up the idle mix a bit try that remember ware it was set

Panhead59

The most common issue with rough idle on these year cars is a vacuum (spelling) leak. With so many lines, and usually old lines , and not always easy to find, vacuum leaks are a pretty common reason for rough idleing.

cardo0

Do u have a spare good carb ready to swap and test? I would recommend this that way u can eliminate the carb as a problem or not right away. I dont know what kind of carb u have but the qjet gets quirky after sitting too long - float hangs up, evaporated fuel leaves deposits over long time. How is your fuel filter?

Disconnect or plug vac lines one at a time.

Are u still using points? If so inspect them.

Hope this helps,
cardo0

Sayfoo

I run a q jet and I think it is jetted correctly (was dyno tuned years ago). Idle may be running rich. It is kinda stinky at idle. I was having overheating problem when I rebuilt the motor on this totally bubba'd car, so I think I let it run a little rich as I tracked down the overheating problem. I do run points, but ignition system seems to be working correctly. Vac advance is all in at about 2600 rpm. Plugs look good. I think the lopy idle is probably because of the slightly bigger than stock cam? I'll lean out the idle mixture.
Thanks for the ideas.