Improperly Installed Intake Gaskets



We noticed the intake gaskets were leaking on cylinders 3 and 4 on the Lycoming IO-320 in an RV-9A. There was a logbook entry by the owner/builder for having replaced them. They were in fact installed improperly, preventing a proper seal.

As you can see from the pictures, the gaskets were installed on the lower side of the flange, instead of between the flange and the cylinder. This not only causes leaks, but will also cause the cylinder to run lean.


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Vic Syracuse
Vic is a fixed-wing and helicopter commercial pilot, CFII with ASMEL/ASES ratings, an A&P/IA, DAR, and EAA technical advisor and flight counselor. Passionately involved in aviation for over 40 years, he has built 11 aircraft and logged over 10,000 hours in 72 different kinds of aircraft. Vic volunteers as a Young Eagle pilot, has his own sport aviation business called Base Leg Aviation, and has written two books on aircraft prebuy and condition inspections.


  1. In the photos there is evidence of an exhaust “Blow Proof” 2piece gasket used on an intake tube and then the other pic shows where the installer missed the intake clamping area “wrong side off intake flange. Some training is needed in both places.

  2. This is great info. I can see the mistake clearly, and I can see how someone would make that mistake.
    Thanks for the tip. I love learning from other people’s mistakes. It’s a lot less painful that learning from my own mistakes.


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