Hi people. I have an intermittent problem starting my Camaro. I have a 383 stroker with an MSD 6AL and Blaster Coil. Sometimes when I go to start it, the engine will just turn over for ages and not fire up. Firstly I changed all the plugs, and it started and I thought I had the problem solved. Then it happened again, so I thought maybe I flattened the battery a bit turning it over too much. So I charged the battery and it started. Then it happened again, so I charged the battery again but it still would not start.
I put the mutli-meter across the battery and it reads 12.66 Volts, is this a reliable indication that the battery is ok or not? I put the multi-meter across the coil input wires and get no reading while cranking, and I have checked and there is no spark.
Finally I was able to start the car with the charger hooked up to the battery to give it a little extra kick.
Does this mean my battery is about to or has already collapsed? I think the battery is about 4+ years old.

Cheers for any input