This isn’t a fuel issue I know it’s ignition.
I keep thinking it’s the crane box but what’s throwing me off is how this missfiring clears up once I take away the vacuum advance.
the vac can does three things, adds timing/shifts RF/increases reluctor gap. Are you saying the problem completely dissappears when the can is capped? something might be loose inside the dist that is being moved when the can shifts. I would cap the can & bump the timing up to where it is when the can is operational & see if it straightens out (grab your dialback). You're sure the RF is close enough when the can is deployed? iirc you said the reluctor gap does not change when the can is pumped up (it changes-gets wider on a regular dist) not sure how this dist is getting around that but it is a good thing). if you duplicate the timing & that ain't it then it has to be something in the dist functioning. (& this is a steady 2500+ miss correct?) EDIT & the can has no vac leak?
