340 Chugging instead of Reving

dartindanno said
I chased an issue like that a couple years ago, turned out to be a bad coil. It idled fine but broke up at mid to high RPM's. On another note try running more initial timing and limit the total timing to 32. If you have an MSD distributor you can change the stop bushing, I think the smallest bushing is 18 degree advance?

Thank you. I have not tested the Coil yet but I'll add that to the list. Certainly sounds like a possibility. The coil is a Mallory promaster 29440 which I believe is specific to this ignition. Something else I need to check before swapping it.