ok bought a vacuum gage today. THe best vacuum I could get by adjusting distributor was 5 inches. Increased idle and got to 15 inches. Not sure if I am doing something wrong or if that is right. My octane selector has retard as counter clockwise and advance clockwise. The distriburor is fully retarded. I am working on a 216 chevy. Had a surge and backfire issue. Now gone. Have slight temp issue. Gets to 200 after 6 miles. flushing radiator now. No thermostat. will put in after i finish cleaning cooling system. Any and all advice appreciated.