I just rebuilt the top end of my motor and put a new cam in it. I tried to start it up and would start but won’t idle. I check the spark plugs and there bad. So I replace those and the wires and ignition coil because I was going to anyways. Now it starts up real well but dies immediately after. I’ve got it to stay idling twice but I drove it for 20 mins or less and it died and wouldn’t idle again once I reached a stop light. Any ideas what the problem could be ?