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At half throttle my CHT's are about the same (250); however, when I go to WOT the #1 cylinder goes to 150 and the others go up to 375. Has anyone else had this happen and more importantly what did you do to fix it?

Thanks
Tom

I know it's not a good answer Tom, but the first thing I'd consider doing is swapping two CHT probes just to make sure that's what's really happening. If the "cold" cylinder changes, you may have a bad probe.

Is the engine still running okay when this happens? Does it start to miss at all?

Sonex calls cylinder #1 the back left one...is that the one you're talking about? Personally, I find it a little unlikely that a rear one all of the sudden gets cold like that, especially if it's fine in cruise power. On my AeroVee the back cylinders generally run a little warmer and leaner at full power as compared to the front cylinders, then things tend to even out at normal cruise power settings.

Any additional information you could provide would be helpful.

Mike,

Thanks for writing back. I just completed my 25 hour overhaul. torquing heads, etc. My first thought was a bad probe. I had to disconnect the probes when I was working on the engine. Maybe one of the leads is not secure as it could be. Why it would work at half throttle and not full throttle is perplexing. The EGT's stayed consistent, the #1, back left, did not drop. I thought there may have been a slight vibration, but it could have been my imagination. I am going to check/change the probes and maybe turn the carb a little bit.

I will keep you posted.

Thanks again,

Tom