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Piston Problem

Discussion in 'Early CJ5 and CJ6 Tech' started by Flak dancer, Jul 30, 2020.

  1. Jul 30, 2020
    Flak dancer

    Flak dancer New Member

    California
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    Jul 30, 2020
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    I'm new here so maybe you folks can help me. I pulled the heads off my 1970 Renegade with the 225 V6 and noticed that all the Pistons on the passenger side of the engine are .020 over and the ones on the left side are stock. Has anybody ever seen this before? and when I put the new head gaskets on is it going to be a problem driving it? I've driven it for about 10 years like that but.... just asking...
    Thanks
     
  2. Jul 30, 2020
    Ohiowrangler

    Ohiowrangler Member 2023 Sponsor 2022 Sponsor

    Newark, Ohio
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    reman assembly line work. Be sure to measure to be sure, not all pistons are marked. Ron
     
  3. Jul 30, 2020
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    The right side of your jeep will be faster than the left side.

    I knew a guy who had a brand new Dodge Hemi back in the 70's. He couldn't get it to run well until they discovered it had a hi-compression head on one side, regular on the other.

    In your case, I doubt it will matter. But I'm no expert.
     
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  4. Jul 31, 2020
    bigbendhiker

    bigbendhiker Member

    U.S.
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    If you hold the throttle just right it will help balance out the tendency of Jeeps to lean to the left. :crazy:
     
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  5. Jul 31, 2020
    Walt Couch

    Walt Couch sidehill Cordele, Ga. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    cordele, Ga.
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    Looking at the firing order for the 225 Odd Fire you will see it fires one side then the other. That being the case I doubt you will notice any diff.

    Oh and welcome to the forum from Ga.
     
  6. Jul 31, 2020
    jeep2003

    jeep2003 Well-Known Member

    Upstate NY
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    Reminds me of the old nascar trick to fool the rules the first two pistons were stock size because thats the ones they check and the rest were over bored.
     
  7. Aug 1, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    We can get an idea of how different this is...

    bore x stroke = 3.75 x 3.4 = 37.5518 cid per cylinder, 0-over
    3.77 x 3.44 = 37.9534 cid per cylinder, 20-over
    (37.9534 / 37.5518 - 1) * 100% = 1.07% displacement difference.

    It's definitely different. Power is roughly proportional to displacement, so the over-bored cylinders are making about 1% more power than the standard cylinders.

    I would guess this is less than the difference between the center and end cylinders, which are a different distance from the carburetor. The end cylinders are typically a little leaner than the center... that's just the way it was before MPI.

    If compression were good on both banks, I'd run it.

    Welcome from Boston.
     
    Last edited: Aug 1, 2020
  8. Aug 1, 2020
    Randy Benedict

    Randy Benedict Member

    Center, MO
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    Jan 13, 2020
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    In the FSM section D-1.1 the engine code number on the side of the block can tell you what oversized pistons were used when original. It only shows up to .010 over. If you have larger, someone may have bored that side. Why? Seems if you are boring one side, you would have done both sides, unless someone overheated it and galled a cylinder and did a bore to just one side. Just a thought.
     
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