Missing / Runs Rough / No Power '71 402
Been a long time, hope everyone is well.
I bought a '71 Impala with an original 38,000-mile 402 and have been chasing a persistent miss since I bought it. Honestly I haven't done much to it other than replace the plugs and reset the timing which was way advanced, about 18 degrees at idle. The issues are a rough idle and general roughness at any engine speed and load (and no power). I've only had it up to 35mph driving around my neighborhood.
The engine looks 100% stock and the heads have been off for a 'valve job' according to the previous owner, although I don't know why that would have been necessary on an engine with such low miles.
I was just looking for feedback on next steps. Seeing that the heads have been off, I was going to pull the valve covers and make sure the valves were adjusted correctly, and check for a bent valve while I'm there. Anything else come to mind?
Chevelles, Camaros, and Pontiacs