Norvel .074 with LESS cooling on glow

Here we have our .074 engine with the cooling fins removed almost entirely. Fuel is Omega 25% and prop is a Cox 8 X 4. A strong run for a minute or so and then a sag. Spraying fresh fuel on the cylinder makes the engine happy again. The overcast gave me cheapo tach troubles but the top end was 11.3K

So, overheating is bad, overcooling is not bad.

The question still remains, WHY did the engine sag? It must be noted that this was a "spare" cylinder in that it was worn out. NO compression snap over when cold. Well, only if LOADED with oil. After a run and even when cooled off, there is no compression to speak of. With the plug out, you cannot feel ANY drag at TDC. None whatsoever.

It's my speculation that the engine is sagging perhaps due to the cylinder growing to such a degree that a total loss of compression and excessive blow by is the result.

The other issue that comes to light is that before the engine sags, we lose our idle completely. No idle below half throttle.

The question is, does idle suffer because of the heat or because of poor compression seal? Past experience leads me to believe that it's the latter.

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