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Today was warmer than the past few days, and I had a slow afternoon at work, so I took some time off and headed to the hangar. I warmed the wrist pin bosses in the piston with a heat gun, then managed to push out the wrist pin with a piece of wooden dowel. Then I stuck my borescope inside and took a look.

Spalled #4 intake tappetThe #4 intake tappet looks pretty ugly. Drat. I managed to get the tip of a finger on the tappet by rotating the crank a bit, and it feels slightly rough, which confirms the borescope image.


I won't print what I said. I've been resigned to finding valve train issues since I first found metal in the oil, but I had been holding out hope that there was a cheaper explanation. At least now I know what the issue is, and what I need to do to get it sorted out.

I'll start pulling the engine on Sunday, and then figure out where I will send it. This is the second time in 3 years with cam or tappet issues, so I'll get the roller lifter mod done this time.


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  • Hi Kevin,

    Lifter spalling: That really sucks. You probably know this already, but engine guru Mike Busch highly recommends Camguard as one of the few additives that seems to be effective at protecting against cam and lifter corrosion.


    Good luck with the Tappet replacement/roller lifter install.


  • Yeah, I know all about Camguard. I've been using it since the first set of cam/lifter issues in 2012. I was really, really hoping that it would make the difference.

  • Well, if you've been using Camguard and it did not help, I'm wondering what one can do to prevent this type of corrosion in any engine. My IO-375 has roller lifters/cams, but my understanding is that such lifter/cams are not less susceptible to corrosion, they simply make its consequences less disastrous. I guess flying often is the key.

    From what I recall, not all Lycomings can be modified by adding roller lifters/cam. Hopefully yours can.


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