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Thread: O-320 Propeller indexing

  1. #1
    Pacer42Z's Avatar
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    Default O-320 Propeller indexing

    I have read several threads (including on the Super Cub Forum) about how the prop should be indexed when installed on my O-320 (160 HP) Lycoming. My prop will go to Sensenich next week for an overhaul. Right now the prop stops on the 12/6 O'clock position every time when I shut the engine down and reading all the threads this is not correct. I know when installing the prop I must put #1 cylinder on TDC and I know how to do it. However, I have read many different opinions on how the prop should be indexed.
    I have a print out from a thread "Engine Vibration" that instructs to mount the prop horizontal to achieve the lowest engine vibration and best position for hand propping. I used to fly a Champ for many years w/o a starter and I always positioned the blade in the 10 to 11 O'clock position to hand prop. I think if you mount the prop horizontal when the #1 cylinder is at TDC the starting position for hand propping sounds about right.

    My mechanic was talking about mounting the prop at the 1/7 O'clock position and tells me this would be the best position to catch the coupler on the downswing. He is the one who has to sign the logbook, but I just would like to find out. What is the collective experience and practice? Any advise is appreciated.

    (All prop positions are from standing in front of the plane)

    Juergen
    Pacer N3342Z

  2. #2
    Zac Weidner's Avatar
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    Default Re: O-320 Propeller indexing

    We indexed our new prop horizontally according to these instructions;

    I think I actually read the same information on some type of Sensenich or Lycoming document, but I can't find it again right now.

    Our prop stops vertically 95% of the time. Occasionally, however, it will stop horizontally for some reason. The engine and prop are both very smooth with this configuration, and the position for hand propping is about right.

    On our Twin Comanche (IO-320 engines), the props are indexed just like the ring gear on the engine; you can only install it one way. They both stop at about 10/4 to 11/5 position (viewed from seat). Hand propping is very hard, though, because it fires about 30 past vertical.


    http://www.shortwingpipers.org/forum...light=indexing


    "Hey, that did't take long.... I found the indexing info in the SWPC useful info. Here it is.

    Propeller Installation on ShortWingPipers

    Remove #1 spark plug. Rotate crankshaft till pressure begins to build
    (place thumb in spark plug hole to feel/hear pressure building).
    You are coming up on TDC for #1 cylinder. Continue rotating crankshaft
    until #1 piston is TDC (use timing mark on back of ring gear aligned
    with crankcase split or use markings on front of ring gear aligned
    with punched hole in starter housing).

    With #1 cylinder on TDC, the prop should be installed such that it is
    Horizontal, ie level to the ground.

    There should be a small "no 1" stamped near the hub on one prop blade.
    That blade goes "over"/"toward" the No. 1 cylinder. It is permissible
    to install the prop "180 out", but only as a "fix" for a SLIGHT vibration
    at cruise. Nine times out of ten, it will NOT be an issue. Torque prop
    correctly (visit Sensenich's website for detailed instructions or see pdf
    file on this site) and safetie prop bolts, reinstall spinner and spark plug.
    Button up airplane. Your prop will now be in the PROPER position not only
    for handpropping, but more importantly will also be "timed" to best act as
    a "flywheel" with the crankshaft.

    Don't forget that this is not Preventative Maintenance, and requires
    a Logbook entry by an appropriately rated Mechanic. "
    Last edited by Zac Weidner; 02-20-2015 at 02:15 PM.

  3. #3
    tloes's Avatar
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    Default Re: O-320 Propeller indexing

    When I took my prop off for overhaul, it was in about the "7:30" position. That was really a bad orientation for hand propping. Even when I was just pulling a prime of fuel through, I dreaded the impulse coupler snap. I was horribly aware of the danger and tried to keep a posture and balance to prevent "the worst". I took pictures of everything orientation-related when I disassembled it all but I'm hoping that my mechanic will agree with the instructions posted here. Horizontal (or barely below it) when firing seems a heck of a lot safer.

    Todd
    Todd Loes -- Waterloo, IA
    (PA22-150 N3568Z)

  4. #4

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    Default Re: O-320 Propeller indexing

    I suggest you don't go by where the prop stops - there is only 1 practical position to install a prop on a 4 cylinder - that is in the normal propping position - coming up on compression at about 10 o'clock as facing the prop and firing about 7-8 oclock - that being said then you can reverse the prop end for end and you will likely find that it is smoother one way or the other end for end - this can be proven doing a running balance before adding any weights.

  5. #5
    Pacer42Z's Avatar
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    Default Re: O-320 Propeller indexing

    Quote Originally Posted by Zac Weidner View Post
    We indexed our new prop horizontally according to these instructions;

    I think I actually read the same information on some type of Sensenich or Lycoming document, but I can't find it again right now.

    Our prop stops vertically 95% of the time. Occasionally, however, it will stop horizontally for some reason. The engine and prop are both very smooth with this configuration, and the position for hand propping is about right.

    On our Twin Comanche (IO-320 engines), the props are indexed just like the ring gear on the engine; you can only install it one way. They both stop at about 10/4 to 11/5 position (viewed from seat). Hand propping is very hard, though, because it fires about 30 past vertical.


    http://www.shortwingpipers.org/forum...light=indexing


    "Hey, that did't take long.... I found the indexing info in the SWPC useful info. Here it is.

    Propeller Installation on ShortWingPipers

    Remove #1 spark plug. Rotate crankshaft till pressure begins to build
    (place thumb in spark plug hole to feel/hear pressure building).
    You are coming up on TDC for #1 cylinder. Continue rotating crankshaft
    until #1 piston is TDC (use timing mark on back of ring gear aligned
    with crankcase split or use markings on front of ring gear aligned
    with punched hole in starter housing).

    With #1 cylinder on TDC, the prop should be installed such that it is
    Horizontal, ie level to the ground.

    There should be a small "no 1" stamped near the hub on one prop blade.
    That blade goes "over"/"toward" the No. 1 cylinder. It is permissible
    to install the prop "180 out", but only as a "fix" for a SLIGHT vibration
    at cruise. Nine times out of ten, it will NOT be an issue. Torque prop
    correctly (visit Sensenich's website for detailed instructions or see pdf
    file on this site) and safetie prop bolts, reinstall spinner and spark plug.
    Button up airplane. Your prop will now be in the PROPER position not only
    for handpropping, but more importantly will also be "timed" to best act as
    a "flywheel" with the crankshaft.

    Don't forget that this is not Preventative Maintenance, and requires
    a Logbook entry by an appropriately rated Mechanic. "
    Zac, this is the same instructions I found and printed out. I couldn't remember where I found them.

    Juergen
    Pacer N3342Z

  6. #6
    SuperPacer's Avatar
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    Default Re: O-320 Propeller indexing

    What Brian & Pacer 24C said!! Although, we may be talking the same "basic position", if you consider that the procedure has you pull a plug & position #1 at TDC (pop now horizontal?). While this is past the desired 10 o'clock position, but in action(with the plug back in, the prop will stop prior to achieving TDC on any cylinder due to the compression finally resisting the rotation. the photo of my Pacer shows the classic "10 o'clock" position, and it always stops there. Your mileage may vary!!

    john
    Arizona Pacer
    Attached Images Attached Images

  7. #7
    Pacer42Z's Avatar
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    Default Re: O-320 Propeller indexing

    Took the Prop off last night and shipped it to Sensenich today for the overhaul. Before I took it off I rotated the engine to have Cylinder #1 on TDC and my prop was pointing horizontal, so it looks like it was mounted correctly. I wonder why my prop always points straight up and down when I shut down the engine.

    Juergen
    Pacer N3342Z

  8. #8
    tloes's Avatar
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    Default Re: O-320 Propeller indexing

    Quote Originally Posted by Pacer42Z View Post
    Took the Prop off last night and shipped it to Sensenich today for the overhaul. Before I took it off I rotated the engine to have Cylinder #1 on TDC and my prop was pointing horizontal, so it looks like it was mounted correctly. I wonder why my prop always points straight up and down when I shut down the engine.

    Juergen
    Pacer N3342Z
    Same story here. Just reinstalled the overhauled prop with #1 at TDC and the prop horizontal. Engine shuts off with the prop vertical. That's really inconvenient on a Tri-Pacer when you need clearance for the tow bar. I'm going to take the prop off (and back home) to let it warm up and apply the Prop Guard tape. When I put it back on, I'll likely return it to the prior orientation (60 degrees "more"). I don't like the idea of the impulse coupler snapping with the prop so low but that's how it was. My A&P said "why would you ever pull the prop through by hand if you have a starting motor?" I was doing it to make it easier on the starter (pulling a prime into the cylinders) but it is hard to argue with respect to safety.

    Todd
    Todd Loes -- Waterloo, IA
    (PA22-150 N3568Z)

  9. #9
    pa20's Avatar
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    Default Re: O-320 Propeller indexing

    a few years ago, I reinstalled my prop with the #1 blade over cyl #1 at TDC, as per the Sensenich instructions. This was against the advise of some of our more knowledgeable SWPO folks. Not only did I find the prop position when stopped inconvenient, there was a prominent vibration during high RPM flight. I put it back the way it was, and no more vibration!
    Mark Ohlau
    PA-20 N7744K 2020 Donation Paid

  10. #10

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    Default Re: O-320 Propeller indexing

    When the piston is fully on TDC - there is no horizontal postion on the flange - so I don't get some of the previous posts - when the piston is fully on TDC the prop would be past horizontal- which is the correct propping postion for a 4 cylinder.

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