Seems like to me...many of us are not wording or expaining what the heck they are trying to do or what they thought was done or went wrong! A test stand is just that...a stand made to hold a engine to test it...NOT BREAK IN. It is fine to test a engine on a test stand, and adjust it if need just a little bit. I say its helps break in to bring engine up to a temp that a run of about 2 min. Shut it down and let it cool completly. Do this a few times and you heat cycled the engine to help faster breakin. I have checked the temps of many short runs on many engines....and seen no overheating. I have a 4 cycle twin that runs within 1- 2 degress measured at the plug. Crankcases and carb intakes run about the same or even cooler than induction air. Hey the average plane and engine installation does not have to checked with all kinds of temp probes ect. Some guys on here are just to darn hi-tect with all the fancy gismos you think everyone else needs. Sure there may be a few special set-ups that need more ducts..ect....but if you read up on the plane and engine combo you are doing...you should be aware of special needs. Take it easy...run em and go fly. Capt,n