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  1. #1

    1200 Non-pv Plug Read

    okay so I finally broke in my SBT replacement short block on my SUV. I still have about half of a tank full of 25:1 or so fuel/oil mixture in the tank. The first picture with the darker plugs are the plugs that I used for the low-speed and three quarter throttle break in.
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    The cleaner looking plugs, at the bottom of the post, were then installed fresh immediately before a 30 second three quarter throttle run leading up into a 30 second wide open throttle run followed by pulling the lanyard to kill it. something tells me that I did not do this test correctly because they're just was almost no evidence on the plugs of anything. what I am trying to accomplish is to diagnose and see if I still have the lean condition that burned out my last motor. I highly suspect it was a WOT lean condition that burned up my new motor in only 4 hours last time. That previous motor was pressure tested and had freshly rebuilt, popoff adjusted to 55psi carbs as well as Osidebill's fuel pump pressure relief modification. I believe that SBT told me the lean condition was on the exhaust side?

    what is the process for checking you're wide open throttle for lean condition?also, if it shows that the plugs are lean after that test does a person open up their high speed adjustment to correct this?

    Okay (3 individual plug pics in middle of post) so here are the same shiny plugs after a 3 mile medium to medium low run followed by a one mile wide open throttle burst ending with pulling the lanyard to kill it. test a decompression after and it still at 121... Same as after the break in. Keeping in mind that the gas is mixed 25:1 or so. To me...they look lean? Click image for larger version. 

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    Last edited by macGruber; 07-30-2013 at 02:57 PM.

  2. #2

    Join Date
    Jul 2010
    I break in my build using 32:1 ratio mix. I think 25:1 is a little too much oil. Also the more oil the leaner it burn as the gas is lesser. I don't think you should goes wot on 25:1 mix. I don't even goes wot on my 32:1 mix during break in.
    As for the wot lean condition test. From what I read and what I did is to use new plugs and go wot for a minute then kill the engine by pulling the safety cable. Then read the plug. And yes, the high speed adjuster control the throttle from 3/4 to wot.

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