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Cylinderliners ovalisation

Discussion in '456/550/575' started by joakim_adolfson, Aug 25, 2010.

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  1. joakim_adolfson

    joakim_adolfson Karting

    Sep 19, 2009
    168
    Stockholm, Sweden
    Full Name:
    Joakim Adolfson
    #1 joakim_adolfson, Aug 25, 2010
    Last edited by a moderator: Sep 7, 2017
    Got some more feedbak on my engine today. Apparently all cylinder liners are within wear limits by some margin with only 1-2 hundreds worn (limit is 5 hundreds), the strange thing is that some liners are oval about 6-7 hundred but only the last 10mm from the top. The really strange thing is that they are oval down the crankcase center line, basically they are bigger in the block length direction that in the normal transverse direction (normal wear spots due to the revolution of the crankshaft).
    This is very strange?? could this have something to do with the fact that the liners are thinner the last 10mm from top in the central line due to be able to sit closer, see pic?

    The top compression ring will enter this area as it sit about 7mm under the cylinder deck.
    Image Unavailable, Please Login
     
  2. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    39,020
    Clarksville, Tennessee
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    Terry H Phillips
    #2 tazandjan, Aug 25, 2010
    Joakim- The only reason I can think would be from end play on the rod bearings or piston pins.

    Maybe one of the pros can chime in.

    Taz
    Terry Phillips
     
  3. joakim_adolfson

    joakim_adolfson Karting

    Sep 19, 2009
    168
    Stockholm, Sweden
    Full Name:
    Joakim Adolfson
    #3 joakim_adolfson, Aug 25, 2010
    Yes all small end bushes have play in them, you can wiggle the conrods back and forth a little. I wonder if this is the slight rattle you can hear in almost all 456 engines running at idle, it's a slight rocking sound back and forth, if so rubbish materials must have been used for the F116 engines (same in 550 as well).
     
  4. mjolson

    mjolson Rookie

    Nov 25, 2007
    3
    #4 mjolson, Aug 25, 2010
    Where the measurements made with a hone plate properly torqued in place to replicate the distortion caused when the head is bolted on?
     
  5. joakim_adolfson

    joakim_adolfson Karting

    Sep 19, 2009
    168
    Stockholm, Sweden
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    Joakim Adolfson
    #5 joakim_adolfson, Aug 25, 2010
    Hej,

    no the measurement was made on an open block.
    The mechanic acctually proposed something similar
     
  6. 166&456

    166&456 Formula 3

    Jul 13, 2010
    1,723
    Amsterdam
    #6 166&456, Aug 26, 2010
    Last edited: Aug 26, 2010
    Strange indeed though I also consider it to be most likely the ovality is caused by the lack of forces from the head. It is not likely this distortion is caused by wear, but that said it may still be a production fault or an overheating occurence once in the engine's life.

    I think you were trying to solve two things, a lower compression on some cylinders and a noise issue. It is most likely you have found the noise issue with the wrist pin bushes and perhaps the main bearings. Worn wrist pins can sound really horrible, especially at idle, much less so with main bearings. Does the lower compression you had on some cylinders match with the slightly oval liners, or not at all?
     
  7. joakim_adolfson

    joakim_adolfson Karting

    Sep 19, 2009
    168
    Stockholm, Sweden
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    Joakim Adolfson
    #7 joakim_adolfson, Aug 26, 2010
    I haven't checked the if the ovality is matching the lower compression on some cylinders, I will do this next week. I'll also verify the valve guides and do a vaccumtest of the heads before I dissasemble it. Still though strange indeed.
     
  8. mjolson

    mjolson Rookie

    Nov 25, 2007
    3
    #8 mjolson, Aug 27, 2010
    I think if you are not using a hone/torque plate and are concerned about these measurements you are wasting your time. I have seen significant out-of-round measurements when taken not using a hone plate. Last motor I had fully machined the builder even properly torqued down the main bearing caps before machining.

    Simple google search brought up this guy's example:

    http://forums.nasioc.com/forums/archive/index.php/t-1213861.html
     
  9. joakim_adolfson

    joakim_adolfson Karting

    Sep 19, 2009
    168
    Stockholm, Sweden
    Full Name:
    Joakim Adolfson
    #9 joakim_adolfson, Aug 31, 2010
    yes you are probably right!
     

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