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- Nov 14, 2007
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I would like very much for comment and incite regarding this most interesting and unusual problem? This engine is the O-290-D2 lycoming with the low compression 6.5:1GPU cylinders, and pistons. These cylinders we did not have any idea of the time since they were overhauled, we just honed the cylinders and lapped the valves. The engine as well as the two rear cylinders #3 and #4 have since overhaul right at 180 hrs of flight time. At 84 hrs of flight time, the #1 cylinder started to fowl the bottom plug every hr or two. It was pulled and another set of new rings along with a different serviceable cylinder was installed, and has worked very well so far. At 172 hrs the # 2 lost all compression due to broken top rings, and a new overhauled chrome cylinder from Gibson's was installed, and has gone approximately 8 plus hrs since, and also the engine has not burned much oil at all since the new cylinder was installed. All of the cylinder head temps are in the mid to high 300's and all of the EGTs run together in the same range, this EGT does not have a temp range it is only a value, and I think is running in the 1300 degree range and has done so for most all of the 180 hrs of flight time.
My question is the #3 cylinder EGT readings are very erratic and jump up and down, it started doing this around 160 or so hrs, and was at first mild, but now has become very erratic. I thought at first it was the EGT probe, and replaced it with a new probe, but that did not make and difference, next I moved the rear probe to the front thinking that perhaps the wiring may be at fault, but it did the same with the # 1 cylinder probe. However the Cylinder head temp probes that screw into the cylinder have al read normal with no obvious change at all. I am thinking I need to change out that cylinder, and that this problem is a precursor to perhaps a valve ready to break off? If any one has experienced the same please comment, and no I have not bore scoped it, nor do I have a bore scope and know how to use it. Dave
My question is the #3 cylinder EGT readings are very erratic and jump up and down, it started doing this around 160 or so hrs, and was at first mild, but now has become very erratic. I thought at first it was the EGT probe, and replaced it with a new probe, but that did not make and difference, next I moved the rear probe to the front thinking that perhaps the wiring may be at fault, but it did the same with the # 1 cylinder probe. However the Cylinder head temp probes that screw into the cylinder have al read normal with no obvious change at all. I am thinking I need to change out that cylinder, and that this problem is a precursor to perhaps a valve ready to break off? If any one has experienced the same please comment, and no I have not bore scoped it, nor do I have a bore scope and know how to use it. Dave
