Have you checked your baffling?

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On Oct 15, 2013, at 7:53 AM, Keith Smith <keith.smith@gmail.com> wrote:

> Hey all,
>
> 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