Timing map when changing cams.

[Harley Pilot]

So how do tuners arrive at a start point for timing  when dealing with a cam change? I understand the part about knock sensors and pre ignition, but how do they decide on a minimum starting point?

[HD/Wrench]

Experience mainly . What type of head is used will give you an idea , comp ratio , and then cam , CCP of set up

So a bathtub 103 head is a faster burn chamber than say a CVO head , S&S head is a very fast burn chamber and thus less timing .

If its an unknown set up you start with something that is close to what you have and work it from there .