Stroke on a 308 2v.... | FerrariChat
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Stroke on a 308 2v....

Discussion in 'Technical Q&A' started by etip, Oct 17, 2007.

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  1. etip

    etip Formula 3

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    #1 etip, Oct 17, 2007
    My motor is torn apart and I'm going to order the new pistons shortly; I have the head cc, head gasket thickness, and an old piston to send to Weisco to get some new, custom 10:1 pistons made. I believe I need the stroke or cyl. volume. Is it the same on all 308 2v or Do I need to bolt some parts back together to get this?

    Thanks for the help....

    etip
     
  2. DGS

    DGS Seven Time F1 World Champ
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    #2 DGS, Oct 17, 2007
    I believe it differs between the US and Euro spec engines.

    The data should be in the 308/QV/328 workshop manual.
    (Due to a disk crash, I don't have my copy handy. (It's backed up to CD somewhere.))

    But the specs differ for different destination models. Is this a US edition engine?
     
  3. etip

    etip Formula 3

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    #3 etip, Oct 17, 2007
    Yes, it is a US car; 1980 GTSi.
    Thanks for the info
     
  4. mk e

    mk e F1 World Champ

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    #4 mk e, Oct 17, 2007
    All 308s have an 81mm bore and a 71mm stroke.
     
  5. 350HPMondial

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    #5 350HPMondial, Oct 17, 2007
    Euro also! (right?)
     
  6. mk e

    mk e F1 World Champ

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    #6 mk e, Oct 17, 2007
    ALL 308s, even euros.
     
  7. 308tr6

    308tr6 Formula Junior

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    #7 308tr6, Oct 17, 2007
    Assuming you can bore a 1980 cylinder (not sure about this), you obviously need to consider that volume change in your calcs. I assume someone has calculated this...for typical overbore increments. Or perhaps you are just installing new spec liners?
     
  8. etip

    etip Formula 3

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    #8 etip, Oct 17, 2007
    If the block hasn't been decked, what is the volume when the piston is at TDC? I thought I read something about 52cc, but I'm not positive. Anyone know??
    Thanks again for all the help.
    etip
     
  9. DGS

    DGS Seven Time F1 World Champ
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    #9 DGS, Oct 18, 2007
    I've only got the tech specs for the QVs and 328, but online I found, for an '80 308 (not sure what model): bore 81mm, stroke 70.9mm, compression ratio 8.8:1.

    (On the QVs, the specs are 81mm bore, 71mm stroke, CR = 9.2 (euro), 8.6 (us))

    Doing the math on the '80 2V, I get a per-cyl TDC volume of 46.8 cc (or 46.9, using the 71mm figure).

    (displacement / ( compression ratio - 1 ))

    ( CR = (Vbdc/Vtdc) = ( X + displ / X -> X + pi * (bore/2)^2 * stroke)/(X),
    solve for X -> X = displ / (CR - 1) = (pi * (bore/2)^2 * stroke) / ( CR - 1 ) )
    (divide bore and stroke by 10 to convert mm to cm)

    Although that leads to the question of whether that "compression ratio" figure is derived, computed, or measured. (The actual degree of compression in the engine will likely depend on valve timing, RPM, and inertial of air flow into/out of the engine.)
     
  10. miketuason

    miketuason F1 World Champ
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    #10 miketuason, Oct 18, 2007
    That's what I'm talking about:)
     
  11. etip

    etip Formula 3

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    #11 etip, Oct 19, 2007
    No kidding. That's why I love this site.... Talk about some info!
     

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