Infinite ohms on a digital ohm meter will look just like it does when you set the meter to test ohms (assuming a multi-meter) without touching the leads together. A new spark plug with no degradation or carbon build-up on the ceramic should read infinite ohms (completely open circuit). Are you using an induction type timing light where you put two leads to the battery to power the light and the third clamp type lead that goes around #1 plug? Sounds like you are and if that is the case you have a bad plug wire or anything in the ignition/distributor.