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  1. #1
    Established Member Two Rings
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    Dec 19 2014
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    Random, possibly dumb compression test question....

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    Can one perform a compression test on a "short block", i.e. engine in the building phase with cyl. heads installed? Someone at work asked me; it's monday, I'm under-caffeinated and not thinking analytically, so I wanted to reach out to the brain trust for a solid answer.

    Thanks in advance!

  2. #2
    Senior Member Four Rings VinnysS4's Avatar
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    Nov 12 2015
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    As long as you have valves installed and pistons I stalled, yes you technically can. However, you'll need the tranny Installed to mount the starter to crank it.. you can however do a leakdown test, assuming the motor hasn't had rings Installed. You need to break In the block to do so.
    And just a fyi... short block= no heads installed. Long block =heads installed

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    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

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    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  3. #3
    Established Member Two Rings
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    Quote Originally Posted by VinnysS4 View Post
    As long as you have valves installed and pistons I stalled, yes you technically can. However, you'll need the tranny Installed to mount the starter to crank it.. you can however do a leakdown test, assuming the motor hasn't had rings Installed. You need to break In the block to do so.
    And just a fyi... short block= no heads installed. Long block =heads installed

    Sent from my SM-N920V using Tapatalk
    Thanks Vinny!
    Yeah, I realized "short block" was a little liberal. The engine in question has the heads/cams installed, existing rings/pistons. I don't know if the timing system is installed however, so that would answer the question immediately, with the exception of cylinder 1 (assuming TDC) : )

  4. #4
    Senior Member Four Rings VinnysS4's Avatar
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    Cyl 8 at tdc.... not 1 on the bhf
    And if the timing chains are not connected, don't even think about running a compression test.
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    Last edited by VinnysS4; 11-05-2018 at 06:03 PM.
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  5. #5
    Established Member Two Rings
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    Precisely! That would negate the need for any further compression testing....



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  6. #6
    Senior Member Four Rings VinnysS4's Avatar
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    Lol

    Sent from my SM-N920V using Tapatalk
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  7. #7
    Senior Member Three Rings Mr.Jetta's Avatar
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    Nov 01 2008
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    Illinois

    Just to piggy back off this brain trust, here... one would manually jump the starter with a battery to initiate said long block compression test?

    If the trans is off, can you turn motor manually to get each cylinder where it needs to be for a leakdown?
    B6 S4 Avant - GWGP

  8. #8
    Established Member Two Rings
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    Yeah, I was thinking this /\
    Iíll be involved in the pre-install process, so weíll give this a try. If turning it manually will work, thatís the tack Iíll take.


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  9. #9
    Senior Member Four Rings VinnysS4's Avatar
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    You can turn the engine manually for a leakdown test. Just put a straw or screw driver into the spark plug hole and turn it until it gets the piston you're working on to TDC. Perform your leakdown test. Move to next cyl. The compression Testing will have to wait until the tranny is bolted up.

    Sent from my SM-N920V using Tapatalk
    1997 VW GTI VR6 (sold), 2003 Audi RS6 (sold), 2010 Audi A4 2.0T (RIP Totaled on 11/2/2015 ) 2005.5 Audi S4

    My build log
    http://www.audizine.com/forum/showth...-s-s4-timeline

    Texpoops "Correct, but a half inch difference isnít going to accelerate wear by much. Iím sure the front dips that much with a fatty in the front"

  10. #10
    Established Member Two Rings
    Join Date
    Dec 19 2014
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    Ah. Makes sense. Thanks for all the input!!!


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