Hello all. Quick question. I just acquired one of those infrared temp guages for r/c engines and so was wondering what head temperature range is acceptable for a warmed up and properly tuned 4 stroke engine? (such as Saito .30, O.S. .70, etc)

Take your own base measurements.

The hottest place on a four stroke is right above the exhaust outlet

With any engine, once you have it adjusted and running well, the temp you measure is the temp you get. Don't rely too much on it. We've found that over-reliance on engine temperature to set the engine's mixture is a sure-fire way to shorten the life of your engine rather dramatically. Sound and performance is the best way to get your engine adjusted properly. Use temperature only as a very rough guideline to help you determine if it's running properly.

If anybody tells you a specific temperature is correct, they're likely wrong. What you read on your engine is the important number. After a while, you'll find what temperature range is about right, and then any deviation outside that range will tell you something's wrong.

By the way, we never use temps to determine if an engine's set correctly or running well.

The factory advice from Bax should be followed 100%. one point is really the KISS principal if cannot see or feel oil coming out the exhaust on any engine 4 strk , 2 strk
or diesel LACK of lube, things will wear pretty quick If the engine is not overpropped and has good cooling over it will be fine . too lean --overpropped --not enough air flow
over the engine. it will have a short life. and of course exceeding the max rpms stated in the directions which is usally caused by under -propping martin

I agree with what all of you stated, however the whole reason behind why I'm asking about the temp range is that if I was building a model of a radial engined plane there would be no issues but project I'm planning will have the engine severely faired in behind a cowling and so I am concerned with the airflow. Therefore even if I have the engine properly tuned and with the right prop it will still not tell me if it's getting enough cooling airflow while in operation (unless it is severely overheating of course). That's why I wanted to get the typical temp ranges for a 4 stroke so that I can monitor the temp while in operation to determine if the engine is getting enouigh cooling.

I do not know if will be of any help but here goes with the engine in a round cowl and even if you have a 'dummy engiine' fill piece of you cut out the area where the engine is to to same size as the cylinder will blend in fine you most however have an opening somwheres twice that area to let the cooling air out martin

meowy84,

This is an interesting question. It seems some engines run cooler than others. I know the exhaust gas temp of a Enya 155 is hotter than any four stroke I have ever run. Hot enough to melt Teflon. The engine was adjusted 200 rpm down from peak and had plenty of air over the cylinder and good flow of exit air about 3x more outlet than inlet.

The only advise I would have would be to get an onboard temp meter like an Eagletree system and fly the engine without cowl and check the temps and then cowl and duct the engine to get about the same temps.