I'm trying to think of a reason a motor will only start with starter fluid being associated with rods, valve train issues. Can't come up with one. Starter fluid is only for emergency not for over and over. Since it fires on the fluid, I will guess fuel delivery/carb/bad gas/big vacuum leak problem. That's the hard start. The knock? Don't know, pre ignition/spark knock/exhaust leak snappy sound or deep mechanical sound? (that won't tell me anything, just wanted to sound like an expert)
P.S. I would want to know if just a semi-fine spray of gas down throat will start it also.
Ran good, you rebuilt the carb, it doesn't run good. "It didn't do it before". You are correct to think it's your rebuild and whatever else you did. Check all manifold pipe plugs, connections, fittings and hoses. Then take carb apart again and re read instructions. Sorry to say all this but I've been there so it's OK. On another post a person was warned about the flange gasket covering Rochester B1 vacuum slot/hole in base of carb. Don't know if that applies to 216.
