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C 90 exhaust leak?

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CubFly

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My new IA completed a compression test. The bore check was also done that looked good. First. I flew the airplane for about 30 minutes. The results were C1-69, C3-68, C4-72 and C2-80. There was a very mild hissing sound from the exhaust when the air was compressed in each of the cylinders - C1, C3 and C4. None during testing C2 that had a reading of 80. I put my palm to cover the exhaust to check whether I could feel any air. There was no feeling of blowing air on my palm but could hear it. So it appears to be mild. There are no intake leaks. While changing the oil after 25 hours, it appeared darker than normal but may not be related. The tach has 68 hours only.

My question is not about the compression but the exhaust leaks. What would you do next if it was your engine? Would you send it to a major engine shop to split the case and investigate? Or take some some baby steps before that? Or these mild hissing sound from the exhaust not worth chasing?
 

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