Hey all. One of the guys at our airport has a Cardinal with O-360 that has high CHT's. He's been running 2100 rpm trying to keep them down but still has issues. He asked me to go up with him to see if it cold run LOP to try and help. I gave it a go this afternoon. Climbed to 9500MSL and had to keep full rich all the way up to keep CHT's somewhat acceptable, for a Cessna. Leveled off and left everything alone for a minute. Set RPM to 2500 and set mixture to 70 ROP. Did in-flight mag check, everything ok. Turned on carb heat and tried to find peak for each cylinder. He has a JPI 700 but has never downloaded it. I think we still have our old JPI 700 cable in the hangar, but have to get software for my laptop again. Found peak for each cylinder manually and noted Fuel Flow. Best spread at 2500 RPM was .9/GPH, 2300 was a full gallon per hour, and 2100 wan about .8/GPH. It was a little hard to get exact numbers with the slight delay of fuel flow indication I assume because of carburetor vs. fuel injection (assuming). His CHT's for 2500 & 2300 were way too high. Like 430-450 on most cylinders. 2100 worked ok for temps but seemed to go LOP just as engine started to stumble. not sure if we should have tried it since spread, with carb heat was over .5/GPH but had to try. Next step is to get my cable and laptop re-setup for the JPI 700 and download a flight making sure recording interval is set to every second. then look at it in spreadsheet mode. Any information that I can forward would be appreciated. Thanks.

Sounds like a baffle problem.

Another trick you can use to get more energy into the fuel/air mixture (for better mixing) is to cant the throttle plate ever so slightly. (Run it just off of WOT, to induce turbulence downstream of the throttle plate.)

But, those temps are too high for that engine. Check the timing (too much timing advance can cause high CHTs). Even if you can get the temps under control by running LOP, that engine isn't setup right, and you might as well chase down the real underlying issue, instead of just masking it. (Could also be baffling, but that would be some terrible baffling to be the sole cause of such CHTs.)