What spark plug to install? (lycoming)

Discussion in 'Lycoming & Continental' started by taff, Dec 29, 2017.

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  1. Dec 29, 2017 #1

    taff

    taff

    taff

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    I wonder if someone can help out with this.

    One of these days I will need to feed the ignition wires through the baffling I am making to the plugs.

    But first I need to buy and then install the spark plugs.
    I went browsing the ACS pages and noticed are many varieties.

    I narrowed it down to Champion and massive electrode (if you want to call it "narrowing down")

    There are 14 results for my narrow down.

    I have a Lycoming O-360
    Please point me in the right direction?
    Thanks.
     
  2. Dec 29, 2017 #2

    Eagle-Mike

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    Look at SI1042AD approved spark plugs. You can download it from the Lycoming website.
     
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  3. Dec 29, 2017 #3

    NDTOO

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  4. Dec 30, 2017 #4

    Bond007

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    Tempest
    UREM 37 BY
    Danny 007
     
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  5. Dec 30, 2017 #5

    taff

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    Great! This is useful information.
    Now let me look closely at my needs.

    *Massive 2 prong electrode (I don't know why 2 and not 3, but why not?)
    * 5/8 - 24 at the ignition wire end. That's what I have.


    *Long or short reach?
    I will need to go stick my finger down the plug hole and find out.
    * Heat range ? No idea!
    What the difference in spark plug and or engine performance?

    Anything that I'm missing? please let me know.
     
  6. Dec 30, 2017 #6

    TFF1

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    What engine specificity are you using or closest type. Things like compression, timing, fuel are going to play in a custom pick. Reach is about the cylinder used. Too long and you can knock a hole in the piston or maybe even a valve hit. Too long also can cause detonation because excess plug will stay hot and turn the engine into a diesel. You have to lay all the specs out.
     
  7. Dec 30, 2017 #7

    taff

    taff

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    I understand there are two reach plugs, long and short. That's the length of the thread that will go into the cylinder right?

    According to the Service Instruction No. 1042AE, long=about 5/8" and short=about 3/8"
    If I measure the thread depth going into the cylinder and find that it's 5/8" then I should use long reach, in my mind.

    I have no idea of the compression, the engine has just been reworked.
     
  8. Dec 30, 2017 #8

    TFF1

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    Yes, there is two lengths. Because the thread pitch is 24 threads per inch, you should be able to tell with a count of the threads in the heads. The threads are pretty deep on the long reach. My guess is you have short. The longs I have encountered have been in turbocharged engines, but there is always exceptions. You dont know if it is low or high compression? The heat range numbers like 32, 36,37, 38, 40 is how well the plug dissipates heat in the chamber. The right range will keep it from fowling but not detonating. Usually the higher the compression the colder the plug. Which O-360 do you have or is the rework different than the data tag?
     
  9. Dec 30, 2017 #9

    PittsDriver68

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    Each engine has a recommended spark plug. For instance the 200hp IO-360's use REM-38E or RHM-38E (the difference is the harness "B" nut).

    Don't bother trying to overthink it. Just look up your engine's specs.

    http://www.championaerospace.com/assets/AV-14-Jan2010.pdf

    Best of luck,

    Wes
     
    Last edited: Dec 30, 2017
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  10. Dec 30, 2017 #10

    Vilhelm

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    Though I am not sure, I think that parallel valve cylinders have short reach plugs, and angle valve cylinders have long reach, but perhaps it is not that simple ?
    Also as Wes says there are two sizes of threads for the harness nuts, 5/8" and 3/4". The large thread plugs for some strange reason are called "All Weather Plugs "
     
  11. Dec 30, 2017 #11

    taff

    taff

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    I think your right!
    I snapped this photo this morning.

    And I have the 3/4" x 20 other end for the ignition leads.
    2 parts of the puzzle in place :)

    DSCN7080 (1280x960).jpg
     
  12. Dec 30, 2017 #12

    ndlakesdreamer

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    IF the overhaul followed normal conventions there should be yellow on the cooling fins near the spark plug hole to indicate long reach plugs.
    You can't use generalities for plug reach, i.e. parallel valve = short reach, angle valve = long reach is not true. I ran two IO-720-A1B's for 15 years, one had short reach plugs, one had long reach.
    Use the SI from Lycoming and find the proper plug.
     
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  13. Dec 30, 2017 #13

    taff

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    The rebuilt motor.

    The cylinders went to one place, the casing to another and the shafts went to another. A mechanic and myself put it together, so I guess this was not normal convention.
    As soon as I figure out what reach plug to use I can either paint yellow or not on the fins.

    One thing at a time. (Without generalizing)

    But I'm still a little confused with the long and short of it.

    I am attaching the same photo again, showing the thread depth into the cylinder.
    I figured this would be ideal for a short reach plug.

    If a long reach plug were installed, I am thinking that the threads of the plug that go further than the threads of the cylinder would get deposited on. This would make it difficult to remove the plug, right?

    This is without thinking that the piston would hit the long plug or not.

    Question. Short reach or not?

    DSCN7080 (1280x960).jpg
     
  14. Dec 30, 2017 #14

    Neil

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    The orange on the cylinder fins indicates a chrome bore. If long reach plugs were required the cylinder shop would have added the yellow on the fins next to the spark plug hole.

    I believe yours is a parallel valve 360, most of which, if not all, use the short reach plugs. Wide deck and narrow deck makes no difference here. I recently had two 540 narrow deck, angle valve airplanes in the shop and one had long reach plugs and the other had short so, as has been mentioned in an above post, the plug reach doesn't follow any particular configuration.

    Champion REM38E would be my guess.
     
    Last edited: Dec 30, 2017
  15. Dec 30, 2017 #15

    PittsDriver68

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    The engine model has not yet been posted. The cylinders go with that, so knowing the model Lyco will answer the spark plug question. Futzing about the number of threads in the cylinder is the long way around. And then you need to understand the heat range of the plug, which is the "38" or "40" part.

    The RH or RE plug type will tell you about the type of ignition harness you need.

    Best of luck,

    Wes
     
  16. Dec 30, 2017 #16

    taff

    taff

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    Thanks for the info Neil.
    Yes, my engine is parallel valve 360.

    Only difference from what you suggested is, H.
    My ignition lead ends are 3/4 - 20 thread.

    So I will probably get R H M 38 E
    H = 3/4-20
    M = short reach
    38= heat range (kind of in the middle of 26(cold) and 50(hot)
    E = Massive 2 prong

    Cheers.
     
  17. Dec 31, 2017 #17

    DHonkomp

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    WOW, I have yet to follow a thread on this forum that contained this much false information, and correct information together. Just use the plugs the parts manual calls for!
     
  18. Dec 31, 2017 #18

    taff

    taff

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    The parts manual...
    Where would I find the parts manual?

    And I thought I was on to a good thing!
     
  19. Dec 31, 2017 #19

    TFF1

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    I think the question everyone is chomping at the bit to ask is where is the data tag, and can we get a picture of it? If no tag, was it put together from a complete engine core, or was each piece bought separately and brought together into one engine. Stuff sent to different shops does not matter as they will figure out what you sent and OH for what it is, unless you tell them otherwise. Inquiring minds want to know!
     
  20. Dec 31, 2017 #20

    taff

    taff

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    It was a complete engine that was taken apart and all sections were sent out for control work and inspection. Pieces were not bought separately.

    Photos of the data tag.

    DSCN7083 (1280x960).jpg

    DSCN7084 (1280x960).jpg
     
    Last edited: Dec 31, 2017

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