Can you properly test for overheating on the ground?

Rotech said we can’t properly test for overheating on the ground. So I guess the prop doesn’t move enough air over the rad and oil cooler when the plane isn’t moving?

Oil and CHT are both above 250. Both went up slowly and steadily the harder I ran the engine. I ran it HARD for about 30 min. 

Carbs, this is what we’re going to check next. The tech rebuilding them epoxied over the check plug to prevent it from leaking. I wouldn’t think this would cause any issues but he was sloppy and may have gotten expoxy where it didn’t belong.

fuel burn is lower by 20-30% 

I haven’t confirmed temp readings. 

 I will check for loose grounds for the gauges.