GalinHdz
Well Known Member
I have been fighting an intermittent hot #3 cylinder on my Lycoming O360 for years and nothing seemed to work. When the problem shows up I have to run the engine quite rich to bring the #3 CHT to just under 400F but at the same time the the other cylinders were at least 50 degrees cooler. Worst still on many flight the CHT's were fine and all 4 cylinders were very close to each other. I tried changing the CHT probe with no luck and my baffling was perfect, or so I thought. Pardon the pun, but this was baffling.
After reading a completely un unrelated thread here on inexpensive borescopes, I bought a Vividia VA-400 Borescope. Out of curiosity I used the borescope and looked into the firewall with the cowl on. I found that, when installed, the top cowl was folding part of the baffling down and almost completely blocking air to, you guessed it, the #3 cylinder head.
You can clearly see it in the picture:
With the cowl top off, the baffles are perfectly aligned with no blockage whatsoever so everything looks good. With the cowl top on, you can't see the baffling near cylinder #3 since cylinder #1 blocks the view. I could not have found this problem without a borescope. I will be "fixing" my perfect baffling so it doesn't get folded over with the cowl top on and do a test flight but I am confident it will drop the #3 CHT by a significant amount.
After reading a completely un unrelated thread here on inexpensive borescopes, I bought a Vividia VA-400 Borescope. Out of curiosity I used the borescope and looked into the firewall with the cowl on. I found that, when installed, the top cowl was folding part of the baffling down and almost completely blocking air to, you guessed it, the #3 cylinder head.
You can clearly see it in the picture:
With the cowl top off, the baffles are perfectly aligned with no blockage whatsoever so everything looks good. With the cowl top on, you can't see the baffling near cylinder #3 since cylinder #1 blocks the view. I could not have found this problem without a borescope. I will be "fixing" my perfect baffling so it doesn't get folded over with the cowl top on and do a test flight but I am confident it will drop the #3 CHT by a significant amount.
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