Setting timing on a 225??

You'll know 'pinging' when you hear it; it is an irregular, light rattly sound. The best conditions to first hear it are low RPM's and accelerating with mid- to wider open throttle settings. Real detonation is much, much louder, like someone hitting an aluminum piston with a hammer.....reeeeally hard. It is unmistakeable and pretty violent sounding. Usually when you hear light 'pinging', you are approaching detonation and it is time to start backing off.

Some engines have a lot of margin between pinging and heavy detonation. The /6 seems to be one so don't be too afraid of it. My '76 Dart Lite with the lean carb would ping all the time but it rarely seemed to progress to actual detonation, and I had to really bog it badly. Others don't give much warning and just detonate; higher pressure turbo'd engines are a typical example.