piston slap...?

Discussion in 'General Subaru Discussion' started by gc8, Jul 9, 2005.

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  1. gc8
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    gc8 Well-Known Member

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    k, so i had a tech from my work align and clean the brakes of my 99 rs. Anyway, he comes back and tells me that i have piston slap. I have never heard of this before, so i came here to read up on it. After searching, ive seen talk about it in the winter, but its obviously not winter right now. People are saying its normal with subaru engines and there is nothing to worry about. Is this true? The tech guy told me id eventually need a new short block, or just a whole new engine. This kinda pissed me off. Also, i had discussed plans on making it into an RS-T, but he said not to now that i have this so called "piston slap". Someone please help me! Is my car screwed? Do i need a new engine? Is there anything else it could be (ive read things about the timing belt)? HELP...i want an RS-T, but i wanna make sure that i have a healthy car goin into this project!
     
    gc8, Jul 9, 2005
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  2. AWDimprezaL
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    AWDimprezaL has more posts than you

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    its normal with wrxs and N/A 2.5s anything else (2.2 1.8) you have problems
     
    AWDimprezaL, Jul 9, 2005
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  3. Deride
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    Deride Well-Known Member

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    run higher octane, I ping on anything under 91 non-oxygenated with my 02 RS
     
    Deride, Jul 9, 2005
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  4. ShortytheFirefighter
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    ShortytheFirefighter Pokemans. I has none. Staff Member

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    My 6 cylinder makes 1250 lb/ft of torque.
    What would higher octane have to do with piston slap?
     
    ShortytheFirefighter, Jul 10, 2005
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  5. rskm1
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    rskm1 Well-Known Member

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    "ping" is premature detonation; lower octane gas explodes faster, and since the spark happens BEFORE the piston reaches Top Dead Center, if the gas explodes too quickly, some of the force of the explosion is wasted shoving the rod down BEFORE it's over the "hump" and on its way DOWN. This causes a metalling ringing sound.

    This has nought to do with "piston slap", which is generally when the rings aren't tight enough or aligned properly, such that the actual bottom of the PISTON bangs against the cylinder wall. This causes a metallic... "banging" sound? This is a very bad thing in most engines. I dunno, is the "boxer" engine design more tolerant of that or something? Why would it be okay in a 2.5 or 2.0 but NOT in a 2.2 or 1.8? I don't really understand THAT statement.
     
    rskm1, Jul 10, 2005
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  6. Todd
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    Todd The Originator Staff Member

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    First I would reclassify it as piston rock...

    The pistons of a 2.5 are very short skirted and do have a special coating to "help" piston skirt wear.

    The hard part is to distinguish between "normal" piston and valve train noise and "abnormal" amount of noise.

    Come, listen to my 98 Legacy GT cold. It has a good amount of "noise". Am I concerned? Not yet.

    You might want to have a technician who has listened to lots of Subaru engines listen to yours (cold).
     
    Todd, Jul 10, 2005
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