340 idle problems

You need more initial. I am running 15 on mine. I had it at 20 with a holley 3310
and swapped in a 670 for better throttle response as I am running a ***** of
a cam that hates to idle at all. The 670 is an awesome carb. Keep in mind it
is wet flow tested also so it is closer to a 750 than you think. I'd work with
the carb. Mine needed a slight tweaking out of the box, and I need to jet it
up a little. Right now I am running 15btdc initial, have the secondarys adjusted to be slightly open to get more air at idle. Putting in a wideband
af gauge today so I can really get it dialed in!

Don't give up on this carb, it's a nice piece of hardware!