Lycoming O-360 CHT1 highest on takeoff (100 deg diff), and lowest in cruise (Data attached)

[nickw9815]

On take off, my CHT1 always overheats the most so I need to pull power back to let it cool down. In cruise, it is the lowest. Lycoming engine is O-360 with carburetor.

I attached data from two flights. CHT 1 and 3 are the hottest by 50 - 100 degrees relative to CHT 2,4. But once in cruise, they are the same or lower by 50 degrees.

Flight 1 is take off at full power, and then once CHT1 hits 450, power is reduced. Climbing at 105kts from sea level to 8,500', then applying full power once we level off. Around 22:50 descent begins.


Flight 2: Full power for take off at sea level. Climbing through ~1k feet, the CHT 1 hits 450 degrees so power is reduced. Gradual climb to 10k, then some maneuvers at 2:15. Steady full power cruise (2600 rpm) at 6,500' between 2:15 - 2:45, then power is changes for remainder of the flight.

 

[nickw9815]

Here is a shorter flight where most of it was at a lower power setting and only 2000'. The CHT's seem to be aligned much better in cruise, but CHT1 is still highest in climb out.

 

[D-Dubya]

Well, you said it "always overheats". Has that been since the day the plane first flew, or is the plane new to you?

Just a cursory look at the data would point to a possible induction leak on your #1 cylinder. The EGT is higher than the others until you reduce the power, then it falls more in line with the others into a normal range. I'd check the gaskets & seals on that intake tube for a possible leak. Your #3 cylinder isn't far behind, so it warrants inspection as well. If you find leaks on those, I'd change the gaskets & seals on all four intake tubes.

Vic Syracuse has a video or two on intake leaks on YouTube, and Mike Busch has written articles on diagnosing intake leaks. If you want to dive a little deeper into the subject, those are a couple of resources you may want to explore.

 

[PilotjohnS]

I found out my cowl inlet ramps were installed to close to the cylinders on the right side. I did some mitigation after osh, but it is still restricting airflow.

Check the cowl cooling ramps are as far forward as possible, especially on the right side.

 

[lipper03]

I’d agree it looks like c1 is leaning out at TO power. Possible Induction leak, agree check Mike and Vic’s comments on that. I can’t remember if they say to do a carb heat check, but that’s another way to see if a richer mixture affects the temps. If an induction leak is too bad, the carb heat may show more then the normal high map to low map check in the air.

 

[D-Dubya]

Here's a link to one of Vic's videos (his maintenance videos are very helpful, BTW):

And here's an article by Mike Busch on troubleshooting with flight test profiles:
https://www.savvyaviation.com/wp-content/uploads/articles_eaa/EAA_2012-01_flight-test-profiles.pdf

Neither of these will take up much of your time and should be helpful.