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PA28 CHTs during climb

Appreciate your input Michael, the gaps you point out has since been sealed with RTV-silicone. I will test tomorrow and let you know how it performs compared to earlier.


So I am still baffled (pun intended) about the high CHTs…

The baffles now are in perfect condition with all gaps sealed with RTV. Cylinders now have 20+ hours on them. Cruise CHT 70% @ 2000ft is around 340F (105-110kts).

One is an Archer II (PA28-181) and the other is a PA28-180 (Challenger), the cowlings are very much the same. It is impossible to climb at WOT without knocking 380, even at IAS 90-100kts it will rise to about 400F+ (during WOT climb).

Now, the cooling is definitely much worse than I thought…, this needs to be adressed properly by the pilots

I will check the calibration of the CHT system, but I doubt they are both much off. Mag timing could also be wrong, and is on the list as well.

Does anyone have any idea how I can check if they carb is running rich enough?


Last Edited by GaryStorm at 01 Oct 18:00

This may have been mentioned before but it’s worth checking the location of the CHT sensor, if you have just one.

I know of one pilot of a big pressurised Cessna twin (421C) who burnt something like a number of tonnes extra avgas during his ownership because – on each of the two engines – one of the six CHT sensors was mounted in the wrong location, so he ended up running way ROP to keep that cylinder’s temperature down, pointlessly.

Does anyone have any idea how I can check if they carb is running rich enough?

I don’t know the answer re the carb but at full takeoff power the engine should be about 150F ROP. The carb settings should be documented somewhere. For example for the IO540-C4 engine (mine) the RSA5AD1 fuel servo is supposed to deliver 23 USG/hr (plus or minus a very small tolerance) at a specific air flow, and the overhauler for the fuel servo will have the equipment to set this up. He will adjust a mechanical stop on the throttle and mixture linkages so that this is achieved, and the way the two control cables are installed then doesn’t affect it. The same procedure must exist for a carb. There may be a procedure for adjusting it with the card on the engine but there should also be one for adjusting the carb alone, as there is with the fuel injection servo.

Shoreham EGKA, United Kingdom
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