Max CHTs?

07-17-2016, 02:38 AM

Allen Low | Max CHTs?

Hi guys and gals/

Question for you. What are max CHTs you let your engine go to? Somehow I thought we should let max be 400, but someone has told me its OK to go to 500.

Said TCDS (Type Certificate Data Sheet) MAx CHT is 500

My engine is IO 540 K1G5



07-17-2016, 11:09 AM


Hi Allen. for Max. engine life I keep my CHT's at 400 or less and EGT's at 1425 or less. FYI: over the years several mechanics have told me that one of the main weakness of the IO 540 are the exhaust valves (running high CHT's and EGT's will likely shorten TBO). JR

07-18-2016, 12:49 AM

mike reibing

Hi Allen

I run my EGT at 1390 and when I do that my CHT sits around 330.

07-18-2016, 04:43 PM

Tony Jurcan | Engine Myths Debunked


Link to excellent article by Mike Busch on engine operation attached.

07-19-2016, 03:54 PM


Tony... Do you have a new link, good.

I have done extensive research with my bird. I have seen cht's as low as 280* and as high as 719*

Downdraft cooling is the best way to cool the engine. Cht's will run around 280-310*.

Of course the openings (62 square inches each), baffeling, and cowling will need to be modified.

One of the biggest concerns is taking off on the water......Nose real high-no air going into the engine.

You really need to talk to Lycoming for the actual specs on the engine. Have your model and serial numbers if contacting them. (500* Max)