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Thread: O-320 Propeller indexing

  1. #11
    Pacer42Z's Avatar
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    Default Re: O-320 Propeller indexing

    I rotated the engine with the top plug removed on #1 cylinder plugging the hole with my thumb. When I could feel the pressure building up from the piston coming up on the compression stroke I kept rotating the prop until the TDC mark on the flywheel lined up with the mark on the starter housing. At that point my prop was horizontal. My engine is sitting this way now until I get my prop back from overhaul so I can put it back on the same way. I checked with my mechanic and he agreed this would be the correct procedure.

    Juergen

  2. #12

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    Default Re: O-320 Propeller indexing

    The timing mark that lines up with the starter is not TDC It is the 25 degrees BTDC for mag timing - that being the case the prop would be fairly close to horizontal - but true TDC the prop is another 25 degrees past that point. That clears up the confusion- thanks

  3. #13
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    Default Re: O-320 Propeller indexing

    Mine is set the same way. Regards the impulse coupling firing, it will fire at TDC, which in my case is prop going thru horizontal. Generally speaking, when you are propping
    it, you will likely have it at about it's top speed about the time it goes thru horizontal. The prop will usually stop before TDC and it is usually in that 100-80 degrees before because that is when pressure is begining to build in the cylinder and there is usually not enough momentum to carry it further. About one in a couple hundred flight will
    mine stop horizontal at top dead center. With a four cylinder with #1 cylinder at TDC, the other pistons are TDC or BDC only. It's the way the crank is made.
    "Progress is our most important problem"

  4. #14
    Gilbert Pierce's Avatar
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    Default Re: O-320 Propeller indexing

    Quote Originally Posted by Pacer 24C View Post
    The timing mark that lines up with the starter is not TDC It is the 25 degrees BTDC for mag timing - that being the case the prop would be fairly close to horizontal - but true TDC the prop is another 25 degrees past that point. That clears up the confusion- thanks
    Hmmm! Mine has both 25
    BTDC and TDC

  5. #15
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    Default Re: O-320 Propeller indexing

    Quote Originally Posted by Gilbert Pierce View Post
    Hmmm! Mine has both 25
    BTDC and TDC
    On the "engine side" of the flywheel I have both marks. I'm not sure on the "prop side" (which is the only side useful with respect to using the starter for indexing). I'm going to have to look when I go back out.

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

  6. #16
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    Default Re: O-320 Propeller indexing

    all mine have both on the front of the fly wheel, never looked at the back
    "Progress is our most important problem"

  7. #17
    Pacer42Z's Avatar
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    Default Re: O-320 Propeller indexing

    I wanted to make sure rather than going by memory, so I went by the airport yesterday on my way home. My flywheel has both marks on the front of it. The 25 BTDC and the TDC mark. When I took the prop off I rotated the engine to the TDC mark when the #1 cylinder came up on the compression stroke and the prop is horizontal.

    Juergen
    Pacer N3342Z

  8. #18
    Brian's Avatar
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    Default Re: O-320 Propeller indexing

    Pictures are worth a lot of words.
    Photo showing the starter ring with prop removed and Cyl 1 on TDC. (Prop Studs Near Horizontal but Not Exactly)
    Photo showing the OEM Bendex Starter relationship to the Starter Ring Cyl 1 TDC Mark.
    Photo showing the Prop Indexed with Steve's recommended 1oclock - 7oclock Index. (Pilots Seat Perspective)
    From this I see Pacer 24 is correct that there is no true horizontal option although close enough for arguments sake.
    Attached Images Attached Images
    Last edited by Brian; 03-03-2015 at 12:28 AM.
    Brian
    Monrovia, CA

  9. #19
    tloes's Avatar
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    Default Re: O-320 Propeller indexing

    Brian: In the last photo, your engine is still at #1 TDC? Or this is after you ran the engine and it stopped in "mid-compression stroke"?

    Best regards,

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

  10. #20
    Brian's Avatar
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    Default Re: O-320 Propeller indexing

    Quote Originally Posted by tloes View Post
    Brian: In the last photo, your engine is still at #1 TDC? Or this is after you ran the engine and it stopped in "mid-compression stroke"?
    Best regards, Todd
    Still at TDC. Avatar photo of me holding the prop is how the prop stops after shutdown.
    Brian
    Monrovia, CA

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