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Our plugs on our 600 hour Rotax 912UL are about due for changing.

A bit of a dilemma:

Took a 16-hour LSA repairman/inspector course from an very experienced Rotax A&P mechanic last year.
He said that Rotax recommends coating threads on plug with a heat transfer compound... thermal paste.
It's usually either a grease with aluminum powder or more comonly silver powder.
Was specific that "if that's what Rotax says, that's what I'd use. Nothing else.

Idea is that by perfect thermal contact at the threads the plug will run at expected design/intended temperatures.

(I'm familiar with that sort of compound... In the computer business, which I'm in, we use it on top of a CPU chip {which produce a lot of heat] to make good thermal contact with the heat-sink that cools/disspates the heat.)

Unlike anti-seize you won't find it at NAPA, but since I'm in the computer trade not hard to get (just shop for heat-sink-thermal-compound.

Anyway, the previous owner who had this rotax for the first 400 hours of its live used conventional sparkplug thread anti-seize compound, and the plugs look darn near perfect even at 200+ hours.

So I'm torn between "do what Rotax says" and "if it worked fine before keep doing what works."

Any info or opinions on this one?


Al
  • Re: Spark plug anti-seize vs heat-sink-compound?

    by » 12 years ago


    Al,

    I use the same heat sink compound you talk about. I get it at Radio Shack. It is a fraction of the cost of the Rotax product and works fine. Also serves as an anti seize. Been using it for several years.

    I'm not really sure of the technical details but I've read that the anti seize compounds are not as efficient at heat transfer as the heat sink products. I did find out one thing the hard way. DO NOT get any on the plug tip. It won't burn off and it will foul the plug.

    Bill.

    Thank you said by: Al C, Irvin Sullivan

  • Re: Spark plug anti-seize vs heat-sink-compound?

    by » 12 years ago


    Use the thermal conducting paste as prescribed in the Rotax manuals. The thermal paste is a silicone based compound. It does as you say, but if you are worried about the anti seize lubing the threads the thermal paste will do the same plus transfer heat. Anti seize does nothing, but lube.
    To me anti seize is an old school hold over that some can not seem to shake. Many of the GA guys at my field are switching and finally coming into the 21st century.
    Remember that Rotax has about 4 million flight hours and millions of dollars in testing and they have good reasons for what they do. So unless someone can show scientifically something is wrong or better my money will still on the expert and proven method.

    Roger Lee
    LSRM-A & Rotax Instructor & Rotax IRC
    Tucson, AZ Ryan Airfield (KRYN)
    520-349-7056 Cell


    Thank you said by: Al C

  • Re: Spark plug anti-seize vs heat-sink-compound?

    by » 12 years ago


    Thanks,

    By the way: RadioShack carries three types of thermal compound.
    Silcon based, ceramic bases, and silver based.

    In my field (computer chip heatsink seating applications) the silver based one would be the preferred one (and the most expensive).

    Based on what Roger said I'd go for the silicon type if you buy at radioshack.

    Thank you said by: Irvin Sullivan

  • Re: Spark plug anti-seize vs heat-sink-compound?

    by » 12 years ago


    Yep, silicon based is what I use. Use it in my 0-200 too.

    Bill.

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