I'm waiting for winter to come around but it seems like my O-360 A1A has been running warmer than usual, requiring me to power back very shortly after takeoff to avoid an excursion north of 425 degree CHT's.

In any case, I know that LOP ops are hard to come by with an O-360 due to poor fuel distribution. Indeed, my #4 cylinder peaks well before the others, making it tricky to get them LOP.

I've been running in two modes...one is around 20 LOP to cool it down to around 385 CHT while the others run just slightly rich of peak. I can do this without much effort, and under a wide range of throttle positions, and density altitudes.

On a recent flight, though, I found #1 and #3 settling on temps that were just too high to be happy with. I would go well ROP to get them cooled, but burned a lot of fuel in the process and still had a warm 4th cylinder due to the fact that it runs quite a bit leaner. This was all done at 75% power or less, btw, density altitude was well above 11k (I was at 11k and it was +10C)

Eventually, I tried something somewhat dramatic. I was determined to get ALL the cylinders LOP. I leaned relatively rapidly and ignored the disconcerting knocking/shuddering associated with the uneven amounts of power being produced between the 4th cylinder and all the rest.

It all happened a bit quickly, but with cylinder 1-3 roughly 20-40 LOP and #4 70-90 LOP, the CHTs dropped like a stone, seemingly in seconds, down to 380-385 across the board for #1-3 with #4 now in the 350-360 range. With careful fiddling of the mixture, and countless experiments with throttle position, I got the vibration down to the point where it was barely noticeable. Eventually it just felt smooth...but I can't tell if I got used to it, or things just settled down, although I wouldn't think it was possible.

Final fuel flow was around 8.8-9.0 gph.

Finally, living the LOP dream with my O-360 :)

I tried repeating this later on, down low and wasn't able to repeat it (ie, never got it smooth).

So, it's elusive, but possibly doable under just the right circumstances. Since I do long trips on a regular basis, I'm definitely interested in making this work.

Separately, I'll try to find out why it's running warmer in general. I did have a mag replaced, the other rebuilt, and 4 new plugs installed in the last year.

Honestly, I'm going to try to save some clams and get this converted to an IO-360 (didn't realize it was relatively inexpensive until my mechanic suggested it), get balanced injectors and run LOP as SOP. The difference in cooling really is staggering. I know I'm probably preaching to the choir, but I thought that O-360 owners might find it eye opening. Get up high and give it a try if you have a 4 point engine monitor. You'll know it's working when your leaning results in EGT and CHT's coming down :)

The trip, btw, was N07-KFTW-KSAV-N07, around 2600nm.

Keith