need tuning help on 340

Get the initial timing and total timing right before you spend 5 minutes adjusting the carb. Timing FIRST!!! 10* is not enough. Only adjustments to mess with on carb are the float level and idle mixture after idle is speed is set. Being a 4 speed makes some of this easier.

JMO, a 340 with a stock cam likes 14-16 initial. If it has any larger camshaft than stock, that initial timing number goes UP. You'll have to limit distributor mechanical advance when giving it more initial so your total number is not out of bounds.

I'd get it warmed up and set initial at 18*, reset idle speed. Shut it off and see if it starts OK when hot. DO NOT drive it hard until you get the total timing number sorted out. The idle should clean up a bit with more initial timing.