Compression test result question (355 GTS -98) | FerrariChat
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Compression test result question (355 GTS -98)

Discussion in 'Technical Q&A' started by johan6504, May 4, 2006.

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  1. johan6504

    johan6504 Formula 3

    Jun 28, 2005
    1,168
    Sweden
    Full Name:
    Johan
    #1 johan6504, May 4, 2006
    Hi
    Got the compression test result on a 355 from a sales person today and it seems a little low compared to what i have seen on the forum. However it seems very consisten over all cylinders. Can anyone comment on this data and tell me if it is ok or not.

    The compression was done on cold engine, which I guess is not the correct way to do it? The Assmeblynumber indicate an engine with upgraded steel valve guides and the car has 20000 miles (32000Km)

    Cyl Bar-PSI
    1 11,4 -165
    2 11,1 -162
    3 11,5 -167
    4 11,3 -164
    5 11,4 -165
    6 11,2 -162
    7 11,2 -162
    8 11,0 -160
     
  2. greyboxer

    greyboxer F1 World Champ

    Dec 8, 2004
    12,709
    South East
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    Jimmie
    #2 greyboxer, May 4, 2006
    My guess is consistency is more important than absolute readings because techniques & settings can differ - promising !
     
  3. johan6504

    johan6504 Formula 3

    Jun 28, 2005
    1,168
    Sweden
    Full Name:
    Johan
    #3 johan6504, May 4, 2006
    That was what I was hoping to hear :)
     
  4. ProCoach

    ProCoach F1 Veteran
    Owner

    Sep 15, 2004
    5,465
    VIR Raceway
    Full Name:
    Peter Krause
    #4 ProCoach, May 4, 2006
    The nearly equal readings indicate an engine that has no sealing issues. That is far more important than the number itself. I would be satisfied with plus or minus 10-12% and you're WAY better than that, even cold (which is not the way to test).

    -Peter
     
  5. tomoshea

    tomoshea Formula Junior

    Dec 29, 2003
    541
    Ireland
    Full Name:
    Tom O'Shea
    #5 tomoshea, May 4, 2006
    if it was cold you would expect lower readings with higher leakage, very consistent though.

    For comparison, a 79 308 I have gives between 158 - 168 when warm across all 8 cylinders.

    Most rebuilders I know say don't worry about anything unless you have a reading below 150 on a warm engine, then you might have a piston ring/ valve seating issue, which can usually be pinpointed using a leak down test.

    For absolute piece of mind I would have someone independent do a leakdown test (not the sales man!)
     
  6. ashsimmonds

    ashsimmonds F1 World Champ

    Feb 14, 2004
    14,385
    adelaide, australia
    Full Name:
    Humble Narrator
    #6 ashsimmonds, May 4, 2006
    looks good!

    only test i've seen better is my silly little fiat, 210psi on all cylinders (+/- 1psi) on 3 different instruments over 2 years.
     

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