Trouble tuning 340.

Lash specs on that cam are probably something on the order of .018 and .022. I wouldn't run them very loose trying to get cylinder pressure out of it. Was the cam degreed? If not, you can probably pick up some cranking pressure by doing that, but there are lots of other things you can do before you go that far to get it running better. What kind of timing curve do you have on it?