[olddog]

The cam is pretty big and it may all be to the cam, however timing may be making it a bit worse. If it is pulling the timing in too fast it will make the engines manors worse. You may want to understand how quick the centrifugal advance is coming in, and how much the vacuum advance is pulling in at what vacuum level.

Too much timing will cause the engine to surge. Some of the power is trying to turn the engine backwards and it gets a bit unstable.