High Compression Head

Discussion in 'Performance Mods' started by geebt48cc, Feb 6, 2012.

  1. geebt48cc

    geebt48cc Member

    Hey gang,

    Ok, what would be the best plug from NGK to run on a 66cc slant milled 135lbs compression? I've been using NGK B6, but it might be just a bit on the hot side when pulling hills at times.......... Any ideas.............................?

    Last edited: Feb 7, 2012

  2. jaguar

    jaguar Well-Known Member

    why do you think it is a bit too hot at times?
    what is the color of the plug?
  3. geebt48cc

    geebt48cc Member

    Hey Jag,

    No, the plug is right at a lighter chocolate color. I've just wondered if I tried a cooler plug than the NGK B6 (like the B7?), if that just might help it run a little cooler? See, I can run it now a good 10 miles +, and you can put your hand against jug for about 5 or so seconds. I can just tell with having more compression, that it runs alittle on the warm side which is normal. Really, guess the only reason I even bring this up, is I'm just trying to see if I can beat the norm of the overall life that these little engines last. I know it is what it is, but just maybe these (want-a-be) engines can full us. It's sitting at right at 500 now.
  4. jaguar

    jaguar Well-Known Member

    I wouldn't change the plug. The heat rating of the plug affects the heat that the center electrode and ceramic gets up to, not the heat of the engine in general. The color is right so leave good enough alone.

    The more power an engine produces the more heat it generates. that's just the way it is. If you start melting pistons then you need to start worrying.

    But if you want to you could do any of these things to lessen engine heat:
    lessen the upper compression ratio
    richen the fuel mixture
    reduce the back pressure in the exhaust pipe
    retard the ignition timing
    make an air scoop for the cooling fins
  5. geebt48cc

    geebt48cc Member

    Ok, I'll leave plug alone then Jag. It's running very well, just need to also get your better coil on it. I wouldn't be surprised if it would also help it to run a bit cooler. In picture below, you can see a top scoop that I haven't tried yet. I'm thinking that this will help quite a bit channeling air on top of cylinder head?!

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