C172 Overhaul

Discussion in 'Maintenance Bay' started by Skymac, Jun 19, 2020.

  1. Skymac

    Skymac Pre-takeoff checklist

    Joined:
    Nov 9, 2015
    Messages:
    120
    Location:
    Kentucky
    Display Name:

    Display name:
    Justin
    Has anyone done a O320 150hp Cessna 172 engine refresh/firewall forward recently? Just trying to get an idea of an average cost. I have an airplane in great shape but it’s getting time to do the engine and prop. Will probably not go a factory reman but instead a smaller shop rebuild.
     
  2. bnt83

    bnt83 Final Approach

    Joined:
    Dec 31, 2012
    Messages:
    9,449
    Location:
    Lincoln NE
    Display Name:

    Display name:
    Brian
    How old is the core? What I understand is that Lycoming "policy" is to not accept engine cores over 30 years old towards overhauled or rebuilt engines, but they do accept them if you buy a "new" engine if you were going to pursue a factory one.

    Probably some of the biggest risk in a field overhaul is the crankshaft. Most all of these O-320s have hollow crankshafts that are plugged in the front but open to the crankcase and they build up sludge in there and corrosive combustion byproducts. There is a good chance your crankshaft may be junk when sent to a repair station for inspection and repairs, a new one is as much as $6500 or so depending on what brand you buy as Lycoming, Superior Air Parts, and Continental Motors all manufacture FAA/PMA crankshafts for the O-320 flavors of engines. Which one to buy is of course the million $ question as it seems like every one of them has had ADs on them at some point. A small shop will likely change order if the crankshaft is bad, and tack on a big expense to replace it.

    I'm considering just buying a new Superior crankshaft which would run about $3800 over the cost of reconditioning my existing crank assuming its even good.

    Being a mechanic and somewhat OCD when it comes to this stuff, and having assembled an 320 before, I am just buying the stuff I want and stock piling it for the big day. I have already replaced just about everything attached to engine so nothing is really old except the core engine things such as carburetor, starter, magnetos, hoses, spark plugs etc, are all much newer and won't be refreshed when the core engine comes apart.

    If you really do it by the ridiculously-overkill-book everything is overhauled or replaced at overhaul, including exhaust, starter, alternator, carburetor, magnetos/harness/spark plugs, hoses, rubber engine mounts, engine control cables. A lot of airplanes really don't need all that stuff done in one shot.
     
    Last edited: Jun 19, 2020
  3. RyanB

    RyanB Administrator Management Council Member PoA Supporter

    Joined:
    Jul 21, 2010
    Messages:
    13,033
    Location:
    Chattanooga, TN
    Display Name:

    Display name:
    Ryan
    The flight school here did an O-320-E2D a few years ago @ Gann Aviation on a ‘75 172M and it was just shy of 23k.
     
  4. bnt83

    bnt83 Final Approach

    Joined:
    Dec 31, 2012
    Messages:
    9,449
    Location:
    Lincoln NE
    Display Name:

    Display name:
    Brian
    Depending on what all they replaced it could be hell of a deal or not. But it sounds in the ballpark of others.
     
  5. Bell206

    Bell206 En-Route

    Joined:
    Oct 6, 2017
    Messages:
    4,137
    Display Name:

    Display name:
    Bell206
    FWIW: engine OH costs can be very location specific due to a number of variables. The costs will also depend on whether you turnkey the whole OH or break into separate tasks like remove/install by one shop and OH by another. Perhaps discuss with your local mechanic first and get their input. From the mx side, I've always found location and local service availability to be the main cost driver in more specialized types of mx like OH or S/M work.
     
  6. chemgeek

    chemgeek Pattern Altitude

    Joined:
    Dec 5, 2009
    Messages:
    2,376
    Display Name:

    Display name:
    chemgeek
    I would expect north of 20K depending on the usability of your cam and crank, not including removal and installation. You never know what is good until the engine is torn down. I did an O-320-E2G about a decade ago at Penn Yan Aero for $19K plus the cost of a new crankshaft. The only reusable item on my engine was the case. I got a new cam, crank, mags, carb, the works. STC high compression pistons were no extra cost. (I knew the cam was shot going in and quoted it accordingly.) The rebuilt engine is a world of difference compared to the one I had. Well-known regional shops can do excellent work if you don't want to go with a factory job. I had used Penn Yan many times prior for cylinder replacement on both an O-235-C2C and my O-320-E2G with good results.

    Good luck. Whoever you go with, make sure you know the quality of their work and their ability to stand behind it if things aren't right. And if you are doing STC work at the same time, ensure they have done it before. Penn Yan knew about my high compression STC and had done many of them before, asking me the right questions about which choices I wanted to comply with the STC upgrade.
     
  7. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,377
    Display Name:

    Display name:
    mondtster
    Perhaps I’ve been lucky. So far 95% of the cranks I’ve sent in for reconditioning have been fine. Based on my experience, I’d suggest having a more optimistic outlook on the condition of your crank because you might end up throwing away a crank that is just fine.

    Also, I’d prefer keeping my older crank if possible. If the crank ADs that have come about on some of the newer cranks in the last 20 years are an indicator of the quality of the newer parts, I’d rather take my chances with old, reworked stuff.
     
    bnt83 likes this.
  8. mondtster

    mondtster En-Route

    Joined:
    Nov 25, 2011
    Messages:
    3,377
    Display Name:

    Display name:
    mondtster
    I haven’t done a 172 o-320 lately, but the last o-320 I did this past winter ended up being about $25k. This included new baffling, starter, carburetor, ignition leads, hoses, oil cooler, engine mounts, etc. Basically everything firewall forward was new.
     
    Skymac likes this.
  9. bnt83

    bnt83 Final Approach

    Joined:
    Dec 31, 2012
    Messages:
    9,449
    Location:
    Lincoln NE
    Display Name:

    Display name:
    Brian
    There was a post on a farm forum from a heavy equipment dealer that said customers seemed always be willing to pay more for a new crankshaft but they didn't really have any better reliability with them
     
  10. idahoflier

    idahoflier Cleared for Takeoff

    Joined:
    Jul 21, 2017
    Messages:
    1,092
    Display Name:

    Display name:
    idahoflier
    All good info above. The only thing I would add is you should probably discuss this with your A&P/IA they probably have a good idea of any extras that would need to be replaced and also be able to give you a ballpark on removal/re-installation if you go with a shop that only does overhauls.

    I would get at least three quotes and make sure you compare each one to make sure you're comparing apples to apples, i.e. new or overhauled cam, mags, etc. and is the machining to new or overhauled limits, they are different. Also consider the warranty.

    I just went through this process about 6 months ago. There were no field overhaul options available for me so I went with Penn Yan. So far 50 hrs into the overhaul and everything good...