I really don't think you need one. I have a 12v that works on 6v, the light is just a bit dimmer and I have an old Sun 6 or 12v that I bought at an auction a while back. I rarely use either. I think the rule of thumb of advancing the timing until you start to get pinging on acceleration then backing it up until the ping goes away is probably the best way. If there really is a BEST way to set your timing.
