What is the normal operating temperature of a gas engine in degrees fahrenheit? If measured by a temp gun, what exact part of the engine should the gun be pointed at? Would the cylinder head where the plug enters be the best spot? Should temperature be taken while engine is running or say a minute or so after engine is shut off? And lastly, does the temperature vary from the make of the engine. In other words would a DLE engine run hotter or colder than a Zenoah, DA, or any other make? These questions are referring to a single cylinder gas air cooled engine only.
Thanks
Mike

They all run pretty much the same general operating temps, which is impacted by your skill in tuning, the way they are cowled, and the way they are operated. 100C to 155C is a good operating temp range. Higher or lower and you're doing something wrong. Don't use a temp gun. They (engines) are not water cooled so they do not operate at the same temperature all the time. A temp gun only provides a rough temperature for the "now".

Do a search for more detailed info. There's a lot of it out there. That you mentioned using an aiming point indicates you're a newbie and therefore need to do some learning.

That's 210 F to about 310 F temperature.

and the "aiming point" should be the plug boss. make sure it is not a shiny surface. Dull black is best. This kind of measurement only is useful when running the engine on a test stand.
The other cheap option would be a venom temperature gage. (use search option). Position the sensor in the airflow shade, against the cylinder wall, underneath the topmost cooling fin. This device records, and holds the max operating temperature so you can read it after landing.
The one and only option is a professional metallic temperature sensor that is underneath the spark plug, using a recording system like many 2.4gHz radios have nowadays.

"With airplanes, keep the pointy end going forward as much as possible."

Thought that was for BOATS!

Where did Pe make that statement?

Aiming point refers to the location a hand held heat gun should be directed to, with is really more applicable to RC cars, not airplanes. The use of a heat gun with RC aircraft for establishing engine temps is not recommended because it provides zero information relating to what temp an engine is operating at during various stages of a flight. An up line runs hotter than a down line. A landing approach runs cooler than any other phase of flight, while a taxi back can run only slightly warmer than the approach phase, but substantially cooler than an upline or vertical oriented phase of 3d flight. Tumbles, hammerheads, tail slides, and torque rolls cause and engine to run quite hot. The temperature delta between one phase of flight and another can be upwards of ~150C. In a poorly tuned and/or cooled engine that delta can be much more, and more than enough to destroy an engine in one flight.

So for RC airplanes a temp gun is quite literally...useless.

Highest temps I've seen in my testing were in tight, high throttle knife edge spins. 5 seconds could raise temp as much as 90* F.

Are there no hobby grade washer type temp probes that we that are not of the landed gentry could use? It seems that is the only temperature that is of use and otherwise hard to take. Thanks.

A Venom temp monitor, available at a lot of hobby shops and, unfortunately, Tower is a reasonable and inexpensive way to go. Not 100% accurate but does provide a relatively constant basis for reference.

Would one of these work? http://www.aliexpress.com/fm-store/5...-dia-14mm.html

But what other electronics is needed? An RTD is a variable resister? Would a good digital multimeter be all that is needed, of course after calibration? Thanks.

So where is all of that going to sit when the plane is in flight and how are you planning on recording the data?

Unless you have a very nice, but also very expensive telemetry system, ala Eagle Tree, the Venom does a fair job by recording the high and low from each flight which is displayed on its screen by pushing a button after landing.

Don't over think it.

Been using venom temp gauges for years now, they are cheap, easy and give you enough data to show how well your are baffling, extraction and tunning your engine.