When tuning with EGT, there is no “one” magic number. Changes in weather, can have dramatic affects on EGT numbers. It is not the number but the trend that is most important. What I mean by “trend” is this. You always wan the EGT to be an increasing number up to a maximum number what ever that may be for that particular day. I like to use both an EGT and CHT gauge to best see the “trend”.
The trend: egt increasing / cht increasing.= good
egt decreasing / cht decreasing = too rich
egt decreasing / cht increasing = too lean.
EGT responds to changes much faster than CHT. Always go richer on the mixture to be safe. If the EGT decreases with richening the mixture, watch the gauge and try leaning the mixture 1/8 turn on the ‘L’ needle. The EGT should increase rapidly from the moment you open the throttle. If the EGT responds slowly then you are too rich.
If you need help with this, call me at 408-569-7317