Hi Ricardo;
I’d like to ask first is you’re sure you’re flying with the mixture LOP?
Since your Cherokee 6 260 is a carbureted engine, it’s very likely that one of the requirements for successful LOP operations–a small spread between the fuel flow when the first of the six cylinders is leaned to peak EGT, and the fuel flow when last cylinder reaches to peak EGT.
By the first and last, I mean the first to peak as the mixture is pulled back to lean the cylinders, and the last one to peak as the mixture control is pulled aft.
In my experience, the fuel distribution to the individual cylinders is so uneven that leaning to get to LOP mixtures will result in very rough and uneven engine operation.
Does your Cherokee have a six cyinder EGT instrument installed?
If so, you can check what’s called the EGT Spread by downloading the “lean test” worksheet from General Aviation Modifications Inc. ( https://gami.com/gamijectors/leantest.php)
Sorry for the diversion.
The advice on the acceptable CHT range for the O-540 engine in your Cherokee 6-260 can be found in the Lycoming O-540 Operators manual. Here’s what it says:
“For maximum service life, cylinder head temperatures should be
maintained below 435°F. (224°C.) during high performance cruise
operation and below 4000 F. (205 0 C.) for economy cruise powers.”
The widely accepted rule of thumb about CHTs is to do what it takes (lessen climb angle, reduce power, richen mixture, etc.) to keep the CHTs below 400 deg F.
As far as your carburetor air temp, it will vary due to the temperature of the out side air you’re flying in.
Some pilots like to add a little carburetor heat, say enough to get the carb temp up to 50 deg F, during cruise. The thought behind this practice is that the warmer air will better vaporize the fuel and create a more homogeneous fuel/air mixture.
Please let me know when you have more questions.
Steve
