ENGINE TUNING
 

I have had to lean my low-end carb needle on an O.S. Hyper substantially. Changes preceeding the need for re-tuning are:

Replaced clunk lines with very small diameter Hayes neopren.

Local temp has dropped about 20-25 degrees F.

How often do you have to change needle settings? What are the usual causal conditions?

RE: ENGINE TUNING
 

Once the low end is set for smooth transition I've never had to mess with it unless I changed muffler style which can sometimes change backpressure etc.

Do a pinch test and get it close, then the rest is by ear looking for smooth acceleration from idle and coming back down to an idle as soon as you hit throttle hold entering autos.