Jason - temperature isn't a major concern with airplane engines. Helicopters yes - but not airplanes as they have a lot of air flow across the cooling fins. As far as a tachometer - I have one, but never used it until I got into four stroke engines. An experienced ear can hear the proper needle valve setting for a two stroke. It's harder to hear on a four stroke. Having a plane engine that idles well is very important as you'll cut the throttle to idle upon approach for a landing, but you don't want it to die and have to do a deadstick landing. Getting an engine to idle well comes through adjustment, but also breaking in the engine per the manufacturers specs.

L