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  1. #1

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    Exactly how does a nikasil cylinder become damaged?

    If you have to use a diamond hone, or remove nikasil then hone & re-coat, then how is it that a little old piston ring can score the stuff? In theory the coating should last forever. Is it a combination of heat and speed that allows the end of an alloy ring or maybe a pv pin to groove the cylinder wall? The aluminum piston puddles indeed, come off with muratic acid. Experimenting with a 220 grit three stone hone (got nothing to lose at this point) at low rpms, seemed to smooth the grooves a bit. ( I can still feel them with a fingernail)
    I know it doesn't change the fact that my cylinders are good only as cores now but I'd still like to understand.


  2. #2
    TennR600's Avatar
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    I havent used a nikasil cylinder for years. When i was building motorcycle racing engines (noughchi kits, GYT kits, and TZ yamaha engines) you had to use a cast iron ring. Not a Alloy!! dont know if things have changed or not but you might have the wrong piston ring.

  3. #3
    SurfRider's Avatar
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    Ok, a little chemistry (for lack of a better term). Nikasil is Nickel and Silicone. For silicone think of "sand". Sand is much harder than steel. When it is first "honed" that is to "cut" the flat surface that the rings will run on. Then they basically "etch" the nickel away from the silicone so that the *only* thing that the rings come in contact with is the silicone, so that is why it is a great "hard" surface ("like glass"). But like anything, you can damage something by lots of force and pressure. When the engine is running normally the rings are making a nice contact with the cylinder walls with only a bit of force. But when you jam a wrist pin, broken ring or some other foreign object against it, it can cause damage. Hope that helps?

  4. #4

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    Thanks for the replies to an old post. I was a little p.o.'d at the time as I had two damaged cylinders instead of just the one that dropped the PV pin. I've calmed down now and am patiently waiting to get them back from Millenium.
    As for TennR600's post, if the rings were cast iron wouldn't they break when you opened them up to slip them over the cylinder into their groove?

  5. #5
    SurfRider's Avatar
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    Yes, you do need to use rings made for Nikasil. There is also Alusil (Aluminum and Silicone) in the old Porsche motors and they required a different ring than the Nikasil rings (ask me how I know). Rings are flexible, up to a point. They have enough give to get them fitted over the pistons without any problems. On my 911 motors, I usually just open them with my two thumbs to get them on. A bit painful, but I have never broken a ring.

  6. #6
    PolarisNut's Avatar
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    Nikasil is short for "Nickel-silicon carbide". And btw, silicon and silicone are NOT the same thing. Silicon is an element, and is what is being used here. Silicone is whats in pam anderson and your caulk gun, but is made with compounds of silicon. Silicon-carbide by itself is a common abrasive used on sand paper and in media blasting. You WON'T touch Nikasil with a cheesy stone hone from sears. As far as rings...some manufacturers use a chrome ring and some just use a cast iron ring, when running in nikasil. The chrome ring is usually only used on the top, since it sees more heat, and is more durable than cast iron, but since it is "harder", it takes longer to seat in the bore. You NEVER want to use a chrome ring in a chromed bore though, but we're not talking about those here.

    Also, if there are grooves in your nikasil plating, its done. Don't bother wasting time trying to hone it. That stuff is only on there .004"-.005" thick.

  7. #7
    SurfRider's Avatar
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    Hey Polars, yes you are correct. I meant Silicon. The actual elements of "sand" are SiO2, whereas Silcon-Carbide is SiC. Si = the element Silica. They basically take sand and convert it to Silicon-Carbide. Here's a link. http://www.answers.com/topic/silicon-carbide. Nonetheless, this stuff is VERY hard and that is why it makes a nice strong coating on cylinders.

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