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Thread: Spark plugs life

  1. #1
    Gordon Misch's Avatar
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    Spark plugs life

    What would be the expected lifespan of massive electrode spark plugs in an O-320?
    Gordon

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    I couldn’t keep three sets healthy much over 400 hours each, then I sold a kidney and went to Tempest fine wires...
    Last edited by OLDCROWE; 04-15-2018 at 09:19 AM.
    Remember, These are the Good old Days!

  3. #3
    Gordon Misch's Avatar
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    Ha! For your 180? Sounds about right for 12 of 'em!! (plugs, not kidneys)
    Gordon

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  4. #4
    S2D's Avatar
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    800 hrs on my tempest before they started giving up the ghost.
    thought they should last til 1000 so I kept trying to save them.
    finally gave up when the plane started sounding like an old John Deere
    I may be wrong but that probably won't stop me from arguing about it.
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  5. #5
    hotrod180's Avatar
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    I've been told that 500 hours is about what you expect out of a set of plugs.
    Although years ago I had a set of Champions on my old C170 that musta had about a gazillion hours on them--
    the center electrodes were worn down until they were a skinny oval shape, and they still seemed to work just fine.
    (Bendix mags BTW)
    My IA finally made me change them at annual time.

    According to Aircraft Magneto Service, most bad mag checks are actually spark plug related.
    Here's a link to a good troubleshooting guide. http://www.aircraftmagnetoservice.ne...shooting-guide
    Plugs are easy to test with a simple multimeter--
    they should read a maximum of 5000 ohms through them.
    New plugs spec out at 800-1200 ohms.

    In my experience, a Bendix mag will spark an iffy plug long after a Slick gives it up.
    Bigger coil = hotter spark.
    Cessna Skywagon-- accept no substitute!
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    In a J-3 they will last forever. The joke here is that I got Greg Madariaga's rejects out of a Cherokee in 1978, put them in my Cub, and am still using them.

    Not so in a mid-to high time AEIO-360. Bottom plugs got "fine wired" two years ago, and the entire personality of the Decathlon changed.

    160 Super Cub down the block got a new engine. One of the partners is rarely in town, and wanted to fly pretty badly, but the lower plugs kept oil fouling. We jumped in the J-3, flew over to the spark plug store, spent $500 for the last four fine wires in town, installed them in 15 minutes flat (he did, under supervision) and zero problems since.

    By the way, even though the Super Cub is his first airplane, he likes the J-3 better. That's one of the reasons we are casually looking for another 1946 with dash 12 engine J-3. We want a semi-cream puff - keep your eyes open for us.
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  7. #7
    Doug Budd's Avatar
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    I am going to try denso iridium auto plugs in my exp cub. Almost have the engine built. catto prop should be here next week.


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  8. #8
    Gordon Misch's Avatar
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    the entire personality of the Decathlon changed
    Bob, could you please elaborate on that? Thanks - -
    Gordon

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  9. #9
    Gordon Misch's Avatar
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    Quote Originally Posted by hotrod180 View Post
    I've been told that 500 hours is about what you expect out of a set of plugs.
    Although years ago I had a set of Champions on my old C170 that musta had about a gazillion hours on them--
    the center electrodes were worn down until they were a skinny oval shape, and they still seemed to work just fine.
    (Bendix mags BTW)
    My IA finally made me change them at annual time.

    According to Aircraft Magneto Service, most bad mag checks are actually spark plug related.
    Here's a link to a good troubleshooting guide. http://www.aircraftmagnetoservice.ne...shooting-guide
    Plugs are easy to test with a simple multimeter--
    they should read a maximum of 5000 ohms through them.
    New plugs spec out at 800-1200 ohms.

    In my experience, a Bendix mag will spark an iffy plug long after a Slick gives it up.
    Bigger coil = hotter spark.
    Thanks Eric

    My plugs, REM37BY, seemed to be running just fine, mag drops of about 75 RPM at 1800 RPM, and no roughness. The gap was large enough that I re-gapped them and had planned to re-install them. 480 hours on them.

    Then I measured the internal resistance as you suggested and all were way high. In fact all but one measured "open". After some reading I learned that Champion changed the resistor design due to high resistance issues. https://blog.aopa.org/aopa/2015/03/1...to-acceptance/ This is a Mike Busch article so I take it with a grain of salt, however it does seem to make sense (other than the tabloid writing style).

    So I took the resistor out of two plugs, and I could see how each of them was arcing to the plug center conductor. Next step, I'm going to see about cleaning up that arc spot, reinstall the resistors, and remeasure the resistance. I'll report back.

    Edit: No change after attempting to clean up the resistor. So - - - ordered new plugs.
    Last edited by Gordon Misch; 04-14-2018 at 04:59 PM.
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  10. #10

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    Personality change? No more searching for fouled plug. No more mag drop during runup. Easier starting. Smoother running. Happier airplane. Much happier pilot.
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  11. #11
    windy's Avatar
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    Spark plugs life

    I had 8 Champion spark plugs, all installed at the same time in my O-360. Right about when the plugs had 500 hrs on them, I happened to have landed on a sand bar on the Wisconsin River on a fly out with a gaggle of Cubs from New Holstein. When we were done on the sand bar, we all jumped in our Cubs & everyone started taking off to head back to NH....except for me and one other Cub that saw I was having trouble starting my engine. Another Cub that had departed came back to help. Lucky for me, both Cub pilots were A&Ps. You find out who your friends are when there’s a snag. One of them had 2 spare spark plugs in his Cub tool bag, not the same ones I was using, but good enough to get a spark going for the other 6 weakling plugs to chime in. Made it over to Oshkosh & got 8 new plugs. All is well.
    Now, I replace 4 plugs every annual (since I fly 250-300 hrs/yr), so the worst case, I have 4 half-used plugs & 4 worn out ones. I carry 2 new spark plugs, a crescent wrench, a spark plug socket, a multi-meter & some anti-seize in a baggie in my Cub tool bag,virtually guaranteeing that I’ll never have that spark plug problem again. Oh, and the new spark plugs are Tempest now.
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    Information for the experimental guys. I quit using aviation plugs a long time ago. I use MSD auto wires that fasten into the magneto caps. This setup was done by Thomas at G3 ignition. I also use the Denso IK27 plugs via a set of 18-14 mm reducers. I just did a comdition inspection on the cub-340 hours and decided to install a new set of plugs even though they looked good, didn't need re-gapped and cost was @$ 8.50 per plug. My engine is 150 hp so to clean the plugs up I will run a 50/50 mix of avgas and 91 octane car gas every 25 hours. Your experience may be different but I've had excellent results with this setup. Larry v.
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    How is radio interference? Are the G3 wires shielded, and similar to Champion wires? I want red wires on my J-3. I know how to do the ferrules on Champion leads, but hate to buy a $400 harness just to shorten half the leads.

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    I'm not sure about the shielding, but it's the same wires used on car engines. I haven't had any type of interference from this setup on the RV-7 or the cub. Thomas at G3 ignition buys this wire in bulk and makes up the harness. I measured each lead from a harness that I had and he used that to make up the harness with the MSD wires.

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    My wires are red but assume other colors are available.

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    Re: shielding. My own auto plugs and wire instructions are specific that wires can’t be crossed or twisted. Similar to auto installations the wires are held apart.
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  17. #17
    Gordon Misch's Avatar
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    I carry 2 new spark plugs, a crescent wrench, a spark plug socket, a multi-meter & some anti-seize in a baggie in my Cub tool bag,virtually guaranteeing that I’ll never have that spark plug problem again. Oh, and the new spark plugs are Tempest now.
    Thanks Windy. Yep, I carry an extra plug also. And my new plugs will be Tempest. An internet search led me to believe that there is no performance difference between Tempest and Champion, and Tempest are less costly. FWIW, Lycoming Service Instruction 1042AF says either engine oil or copper-based anti-seize on the plug threads. So maybe no need to carry anti-seize??
    Gordon

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  18. #18
    windy's Avatar
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    I had a stuck spark plug one time that pulled out the helicoil when it finally came loose. The spark plug inspection turned into a little trip to the cylinder repair shop. Anti-seize is cheaper.


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  19. #19
    Gordon Misch's Avatar
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    Yikes! I've always used copper anti-seize myself.......
    Gordon

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    My IO-550 came from Continental with a box of Champion iridium fine wire plugs. Somewhere in the paperwork I read that these plugs should last to the TBO of the engine. They had better last at $1278 for a box of 12.

    When I was a young squirt, my old timer boss told me to use a drop of engine oil on the threads. I've been doing this for 55+ years without ever having a plug seize in the cylinder.
    N1PA
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  21. #21
    Steve Pierce's Avatar
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    I have been seeing 500 hours on factory new 180 hp engine with CHampton spark plugs using their no go gauge. More than double that with Tempest fine wires.
    Steve Pierce

    Everybody is ignorant, only on different subjects.
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  22. #22

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    Quote Originally Posted by Gordon Misch View Post
    Ha! For your 180? Sounds about right for 12 of 'em!! (plugs, not kidneys)
    Did the 180 when replacing cylinders and the cub at last years annual both with Tempests and would have put them in the cub sooner but couldn’t get them at the time, I won’t go back to massive’s as both engines run smoother and there is essentially no plug maintenance!
    Last edited by OLDCROWE; 04-15-2018 at 09:29 AM.
    Remember, These are the Good old Days!
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    Quote Originally Posted by bob turner View Post
    In a J-3 they will last forever. The joke here is that I got Greg Madariaga's rejects out of a Cherokee in 1978, put them in my Cub, and am still using them....
    Not sure why type of aircraft plugs are in would make a difference. Magneto model does though- like I said before, IMHO a Bendix will spark iffy plugs long after a Slick gives up on them. My joke to a buddy of mine is that a Bendix mag would spark a carrot, if you figure out how to attach the leads to it.

    Like Gordon pointed out, resistors wear out. I understand that resistance increases a tiny little bit, every time the plug sparks.
    Eventually there's too much resistance to overcome- even for a Bendix.
    My favorite uncle worked as an A&P up in Alaska in the 40's & 50's. He told me that you used to be able to buy replacement resistors for spark plugs.
    I guess Champion or whoever must have realized that there's a lot more profit in selling a $20 spark plug than a 50 cent resistor.

    I had an experience once in my old C170 similar to Windy's.
    It had been getting a little hard to cold start.
    It was springtime and I figured that I just needed to adjust my starting drill for warmer weather-- less priming, whatever.
    Then one day it stranded me (luckily just at a nearby airpark) when it just flat ass refused to start.
    Finally got it going the next day, flew home and pulled the mags (Slicks) to have them checked.
    They were fine. Within Slick specs, anyways.
    A dozen new plugs solved the problem.
    Cessna Skywagon-- accept no substitute!

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