o-360

I know this is an old post...but if you have the 10-3878 P/N carb there is nothing you can do to prevent these high CHTs on #3 and #4. Verify that if you have the 10-3878 that it has an "M" stamped on it...meaning it had the re-jet field mod. Marvel Schweber put out a service bulletin for high CHTs back in 1962. The main jet is too small for this engine. Or...you can install the newer 10-4164-1 carb that has the mod already. My CHTs went from 440+ on climb out to <390...and during level off they dropped the same temp as the front ones...330. All from swapping the carb to the 10-4164. Jim

Just to let everyone know...anyone with the O-360-A1D needs to verify their carb is either the 10-3878 stamped with an "M" or the 10-4164-1 carb. I had high #3 and #4 CHTs for years and couldn't figure it out. Finally, I came across the Marvel Schweber service bulletin from 1962 for the Mooney M20B and M20C. It stated that the carb for these engines needed that modification kit to re-jet the carb which was a field A & P mod...and then the carb was stamped with an "M". the 10-3878 carb will NOT put out enough FF for this engine. Researching further, I discovered the upgraded carb for this engine was the 10-4164-1 which puts out almost 18 GPH on takeoff. I had checked timing, baffling, adjusted climb out procedures, etc...all in vein. My #3 and #4 CHTs would quickly climb to 440+ before I even reached 2000 feet. I installed this 10-4164 carb and problem was solved!!! I did my first max climb to 2000 feet, 1100 FPM, full throttle, with airspeed all the way down to 70 kts. CHTs never went higher then 390! It was like night and day. I also had previous problems with the 10-3878 carb like engine knocking in cruise (similar to a fowled plug). Turned out it was pre-detonation from the engine running WAY to lean. BTW...I have a Cherokee 180 with engine & CSP mod (O-360-A1D). Jim

I am still perplexed? Your posted engine monitor report showed the high EGTs on #3 tracked proportionality to the high CHTs? Jim