So, I'm heading out to Johnson Creek today in the C-180. The engine is pretty new, under 300 hours. Runs like a clock. While I am flying along at 8500ft getting close to flying over Yellowstone and other less friendly terrain than the giant flat runway I have been flying over for the last 500 miles, I notice that my oil temp has been creeping up a bit. Not really high, 188 or so, but a little high for cruise. I turn the money knob in a crank to give a little cooling and go back to staring out the window. Then I look down at the EI UGB 16 and see that cylinders 2, 4, and 6 are all 100 degrees lower than 1, 3, 5. I have the UGB "normalized" so it makes a nice flat line when things are going along fine. Well, the flat line went away. Engine still running like a top. EI of course is closed, so no help there.
So I called Steve Pierce, the guy who built the engine, and the only thing that we can come up with is an intake leak on one side. Only problem with that theory is that the O470 has a circular intake system, it is not branched. Oh BTW, the CHT's are PERFECT. Within 25 degrees of each other or less - this is a carburatored PPonk engine. Now, I have to admit that while I THINK that the EGT's on 2,4,6 dropped, it could be that the 1,3,5 EGT's went up.
I did a test flight before decided to RON in Riverton, WY this evening, with a plan to pull the cowl tomorrow and look at all the intake and exhaust stuff.
Even though everything was working perfectly, the little voice told me to check it out further (no it was NOT Laura's voice, although she was in agreement).
Any ideas folks?