Tom’s top ten list of things to check when diagnosing your engine
1. Check for vacuum leaks at the gasket between the manifold and head and also around the carb base.
2. Check idle vacuum at manifold– should be 15 – 20 inch Hg. and steady.
3. Check for carb flooding or dripping at idle by looking down the carb throat with a good flashlight. (air cleaners removed).
4. Check ignition initial timing – should be approximately 10o B.T.D.C. with vacuum advance unhooked.
5. Check vacuum advance function – will the diaphragm hold vacuum?
6. If you have a distributor with points, check upper bushing wear by pushing the rotor “north to south” and then “east to west”. If you have an HEI, check rotor-to-cap terminal alignment at cylinder #1 firing.
7. Check individual cylinder power at idle by pulling each spark plug wire and note RPM loss for each cylinder.
8. Check cranking compression (with throttle open).
9. Are all the rocker arms going up and down? Check lash.
10. Check for internal crack or hole in intake manifold heat chamber.