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Thread: What would cause THIS??

  1. #1
    aaronb
    http://www.id10t.org/albums/broken/DSCN0027.sized.jpg
    http://www.id10t.org/albums/broken/DSCN0028.sized.jpg
    http://www.id10t.org/albums/broken/DSCN0026.sized.jpg
    My initial thought is this.. Head gasket problem caused by too much water pressure coming in from my pump. Water in cylinder->broken pistons->bent valve.
    Rings and gaps look OK...
    Thoughts?
    Thanks.
    -aaron

  2. #2
    Jeremy1Kanobe
    That exact spot is the weak link in the BBC piston. The intake valve relief comes very close to the top ring groove. Often times there is less than .030" in the closest spot. You are saying the rings looked fine? Not butting? If this is really the case then you are fighting with detonation. Real problem for boats(always under load). How to solve? 1. Shallow the intake pocket. 2. Backcut top ring. 3. Move top ring down. I give this in the order I would approach it. Looks like a JE shelf part. At least you can order those 1 at a time.

  3. #3
    BIGCHRIS
    whats your timming set at looks like possible detonation .DO you have nitrous on the motor

  4. #4
    Hallett19
    yeah, with the color of that cylinder,looks like it warmed up a bit. Check timing or fuel delivery. Lean out a cylinder, heat it up, break stuff.... sorry to see that though. How did it start running when you noticed it? Did you ever notice a detonation sound ? I know its hard to hear with boats.

  5. #5
    aaronb
    It was running great all day long. We were floating for an hour or so, and then I started it up to head back down river. All of a sudden, I heard it backfire a couple times (like what happened last year when I broke a rocker stud). I didn't hear anything else, though. Once it did that, I shut 'er down... and floated to a sandbar where I pulled a valve cover and noticed the bent valve.
    No nitrous. I don't recall the exact timing numbers.. My buddy set it for me when I wasn't around. Maybe I should blame him.
    It was running fine for two lake trips and all day on Saturday at the river.
    -A

  6. #6
    GofastRacer
    From the pic it looks like that cylinder leaned out big time!..

  7. #7
    wsuwrhr
    Looks like 2-4-6 are WAY lean.
    Has the gas been sitting all winter?
    How is your fuel pressure?
    Fuel delivery problem.
    Brian

  8. #8
    Jordy
    Looks like 2-4-6 are WAY lean.
    Wouldn't that be 4-6-8???
    What do 3-5-7 look like, as well as 1 and 2????
    That's detonation in it's finest form.

  9. #9
    Carnivalride
    Wouldn't that be 4-6-8???
    What do 3-5-7 look like, as well as 1 and 2????
    That's detonation in it's finest form.
    Jordy look where the starters located, wsuwrhr is right 2-4-6 are the lean ones 8 still has carbon on it.

  10. #10
    wsuwrhr
    Wouldn't that be 4-6-8???
    What do 3-5-7 look like, as well as 1 and 2????
    That's detonation in it's finest form.
    Uh huh, and to think EVERYONE has a chevy.....
    This coming from a Mopar guy.
    Brian

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