It was about 10 years for mine. When it started it was one of the sweetest sounds that I ever heard!
These old sixes like lots of choke to get up and running. When you are trying to get it going, hearing the starter speed up means it is getting a little help from the motor! It will probably do that a bit and then catch. Make sure that you have a bit of throttle too. Normally the cam on the choke link will supply that.
