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Thread: Low compressions in (2) cylinders..

  1. #11
    grbamford's Avatar
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    Default Re: Low compressions in (2) cylinders..

    My mechanic is going to pull the covers and inspect the cylinders this morning. The engine is an O-320 Narrow Deck with apron, 1875 hours SMOH. I appreciate Troy's candors about engine usage. Unfortunately, I am that guy. No excuses being made because we have all heard them. I make 25-30 hours a year on the plane and most of them are from March - October. I know that isn't the best profile for an engine. Once he comes back with an idea of what they look like I will let you know and hopefully have a few pictures of them to share.

    I appreciate everyone else's comments. This is the first time that I have heard that low compressions is not necessarily the end all of engine health. Once the airplane comes back from the annual my plan is to run the plane at 2450 for ten hours and redo the compressions. I only have one instance where I thought the plane wasn't producing the power it should have. End of Aug I took the family camping (Wife, 9yr old and 8yr old),camping gear and a full tank of gas. Temps where in the 70's. DA was 1700ish. Took off in under 1000 ft. The next morning We reloaded with all of our gear and 3/4 tanks of gas, temps in the 50's and DA around 700' on a grass strip. Took off around 1800 ft and was sluggish on climb out. Low airspeed, flat nose attitude and sluggish to accelerate to cruising climb. It just felt wrong.

    I had to replace the #3 cylinder a few years ago due to worn exhaust guide valve while flying the airplane from California to Va. Given the age of the engine and time on it, I wouldn't be surprised if that where the case here again.

    Greg
    Last edited by grbamford; 10-14-2020 at 10:58 AM.

  2. #12
    grbamford's Avatar
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    Default Re: Low compressions in (2) cylinders..

    These are some borescope photos from this morning.

    IMG_4485.jpegIMG_4486.jpegIMG_4487.jpeg

  3. #13
    siouxpilot77's Avatar
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    Default Re: Low compressions in (2) cylinders..

    This is a great thread!


    Sent from my iPhone using Tapatalk

  4. #14
    Marc Davis's Avatar
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    Default Re: Low compressions in (2) cylinders..

    To evaluate the valves you need a picture showing the whole valve face to look for symmetry.
    Looking behind the intake and exhaust valve will tell you more about the valve guide health.

    Another plug for the videos put out by Savvy Aviation. They increased my understanding of engine evaluation dramatically.

  5. #15
    Marc Davis's Avatar
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    Default Re: Low compressions in (2) cylinders..

    In my opinion, every aircraft owner needs access to this tool.

    VIVIDIA ABLESCOPE VA-400 INSPECTION BOROSCOPE

    https://www.aircraftspruce.com/pages/to/scopes/vividia12-04891.php

    scope.jpg

  6. #16

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    Default Re: Low compressions in (2) cylinders..

    Quote Originally Posted by Marc Davis View Post
    In my opinion, every aircraft owner needs access to this tool.

    VIVIDIA ABLESCOPE VA-400 INSPECTION BOROSCOPE

    https://www.aircraftspruce.com/pages...ia12-04891.php

    scope.jpg
    I agree.

    They run around $200, but you can find them at trade shows and/or on sale for $150-$175.

    Then use the extra money for the Airbox wireless attachment, it makes it easier to use.

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