Too much timing?
Assuming that 20 initial is at 850 rpm and lets compare to a Chrsyler built MP distributor with the initial set at 12* at same rpm.
IF there are two primary springs, whgich would explain the advance not moving until 1100 rpm, maybe the timing looks like this.
it might be a little weaker at idle, but in low speed driving feel really good. It probably will even be OK with vacuum advance, except maybe on the highway or interstate. just generalizing here
And if that same advance was set at 14* 850 rpm, the engine might respond a bit like an old dog (assuming the Mopar Performance advance is close to what the engine wants).
The shape of the advance curve matters!
here's why I'm suggesting you measure the advance.
Assuming that 20 initial is at 850 rpm and lets compare to a Chrsyler built MP distributor with the initial set at 12* at same rpm.
IF there are two primary springs, whgich would explain the advance not moving until 1100 rpm, maybe the timing looks like this.
it might be a little weaker at idle, but in low speed driving feel really good. It probably will even be OK with vacuum advance, except maybe on the highway or interstate. just generalizing here
And if that same advance was set at 14* 850 rpm, the engine might respond a bit like an old dog (assuming the Mopar Performance advance is close to what the engine wants).
The shape of the advance curve matters!