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  1. #1
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    Member No: 75069 g57yle is an unknown quantity at this point g57yle's Avatar
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    one question for someone clever! and experienced

    when i start my engine in the morning it runs nice but if you rev the engine slightly it makes a slight knoking noise but if you keep it revved it goes away. this happens even at 1000rpm! when it warms up it compleatly disserpears. sounds like its coming from the bottom half. is it because of the low compression? 7.5:1? or could it be something else. the bottom half is currently a 325i block, 525e crank, conrods and cut down 525e psitons. so really its all 525e. apart from that its sweet!Thanks in advance

    G 57YLE MOTORSPORT inc


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    Re: one question for someone clever! and experienced

    probably piston slap. You should let the engine warm up until you give it any boost or revs. The silicon impregnated pistons need to expand in order to fully seal.

    Just my guess.


    RevHigh E39 performance parts for sale

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  3. #3
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    Re: one question for someone clever! and experienced

    thats exactly what i do. i let the car warm up compleatly before driving fast. do you know if that can damage my bores or pistons? or yould it be ok? thanksThanks in advance

    G 57YLE MOTORSPORT inc

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    I would imagine you...

    replaced the rod bearings, bolts, lifters when you built the engine, correct?

    What viscosity of synthethic oil are you running?

    Tensioner pulleys may need inspecting as well.

    I'm just throwing out some quick ideas on sounds that can come from the engine that are cheap fixes or are free.

    Good luck!




    RevHigh E39 performance parts for sale

    "By ignoring this revolution and avoiding the changes that are inevitable, you leave your future at risk."



    Just a' good ole' boyz tune

    The General's horn

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    last dyno sheet more to come N/A

  5. #5
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    i changed all the possible bearings

    as long as its just piston slap and the engine doesnt get damaged im ok with it.Thanks in advance

    G 57YLE MOTORSPORT inc

  6. #6
    matt325is
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    Re: i changed all the possible bearings

    I wouldn't worry about it, mine does it too when its colds, then goes away. I know of many people who have aftermarket piston setups who do that. A lot of times its because if the stroke and rods are too long, the piston/skirt is quite short, and can tilt a little bit when its not expanded. Just keep it cool when its cold, then let her rip when its hot...

    matt

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    thanks matt

    that exactly what i dooo! i drive really slowly at first until it reaches normal temp. then im gone! what psi are you running matt and what are your specs? thanksThanks in advance

    G 57YLE MOTORSPORT inc

  8. #8
    matt325is
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    Re: thanks matt

    http://matt325i.home.comcast.net/Webpage/turbo.html
    266whp and 273wtq at 12psi.

    There are the specs for my car, I am about to weld a 3" exhuast to replace the restrictive 2.5" exhaust (with cat.. bah). Hopefully that will free up some flow, and maybe a little more tuning can hit 300+whp.

    matt

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