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O-540 Overhaul begins

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  • O-540 Overhaul begins

    I had bought an O-540B4B5 core on EBAY several years ago. It was 2800 hr never opened up out of a Cherokee 235. Back in March one of our local EAA chapter members brought John, a retiree with 27 years experience building engines at Western Skyways in Montrose, CO. He has opened his own shop where he does all kinds of work and charges $35/hr. Today I assisted him in taking my engine apart. He was astounded at how good everything looked considering the time on the engine. We checked the crank dimensionally and for runout, it is still within new limits, won't even have to be ground. Cam shaft appears to be repairable. No visible fretting on the case halves which is unusual for a narrow deck engine. Have a couple accessory case gears that will have to be replaced. Hopefully dye pen and magnaflux won't turn up any issues. Appears that Western Skyways will be able to perform any necessary work on case and crank, and balancing everything. I just bought new Lycoming cylinders and they are on their way to Ly-Con for CNC port and polish and installation of their 9:1 pistons. When I receive them will be ready to install with no further work. Hopefully in about a month we will have all the parts back and be ready to put it together. The only thing I need to buy still for the engine is one magneto. I learned a lot today. I feel very good that John wouldn't okay any part in the least bit questionable. It will be an experimental engine but built to certified specs.

  • #2
    Great - very educational doing it yourself, I bet it will be a pleasure too.

    For my 2c, I would definitely replace the cam shaft while you have the engine open. It seems to be the weak link on well used Lycoming engines, particularly ones which have sat unused for several years. There's no telling how bad the inter-granular corrosion will be on the lobes, and you can't necessarily grind it out or even detect it until the part starts to fail prematurely. Replacing the cam shaft is the cheapest insurance you can buy.


    • rodsmith
      rodsmith commented
      Editing a comment
      I'll talk to John about the camshaft again. He had originally indicated new was the way to go until he saw how good this one was. He also mentioned something about it having a better cam profile (higher lift) than the new ones. I looked at the logs again, engine was new in 1963, lycoming does a lot of things different now, meaning some parts have to be replaced just because they are obsolete. One example was the rod bolt nuts are secured with roll pins. The rods will require some minor machining for the new style nuts.
      Last edited by rodsmith; 06-12-2018, 11:07 PM.

    • Battson
      Battson commented
      Editing a comment
      At expert would know best. If your engine is from the desert then corrosion may not be a key concern.