new motor blues

Ok with the engine at idle, place your timing light on each spark plug wire. if you find one which does not make the light flash, there is an ignition related reason like a bad wire, carbon tracked cap etc. If all 8 plugs cause the light to flash, there is some other reason why the cylinder isnt hitting. Th check for an internal vacuum leak, place your hand over the oil breather (not PCV ) so the crankcase builds a vacuum. You will feel the vacuum build. If the engine smoothes out, you have an internal vacuum leak, caused by a bad intake gasket, damaged or cracked manifold, etc. With 166-170 psi cranking compression, you have good valve and ring seal. Should be no need to pull heads off for years to come.