ORIGINAL: flhyr
no leak test performed but I did ''re-break in'' the engine on the ground without issue. (without the cowl) But I've also run the engine on the ground with the cowl for a full tank without issue.
Did you ever hear a ping noise?
When you ran in on the ground....was it at full throttle?
If I were you I'd fly it without the cowling and see if that helps.
Write down the list of variables and start with the easiest, cheapest ones....and eliminate them as you go.
If it is detonating..you're going to have to lower nitro, lighten the prop load, or add a head shim or two.