Removing carbon deposits? - Page 2
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  1. #21
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    Porting a head without a flow bench is a good
    way to make a very expensive ashtray.

    [img]smile.gif[/img]

    Sometimes smoother is not better - that is, it
    does not flow more air.

    My comments about the carbon were made to make
    folks think - if the carbon is back there after
    an hour of running, does it really *have* to
    come off during the re-build?

    Why is the carbon there in the first place?

    What would you thing if you opened the head
    up, and found the aluminum in the head, and on
    the piston crown, completely free of any carbon
    at all?

    Jim

  2. #22
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    Jim asked;

    "What would you thing(k) if you opened the head
    up, and found the aluminum in the head, and on
    the piston crown, completely free of any carbon
    at all?"

    I would think you were burning Methanol, had very high compression and the combustion process did not include any engine lubricating oil, which is essentially impossible.

  3. #23
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    Jim,

    "Porting a head without a flow bench..."

    I knew that my post was going to open a can of worms. Head porting is probably the most controversial subject in the performance arena. A flow bench is great, if I was designing my own custom heads from scratch or if I was trying to sell misleading big flow numbers. I don't think that MitsTech's cylinder head is a one off super high performance master piece. Smoothing out the casting imperfections would hardly turn it into an ashtray. It would more than likely improve flow from the stock condition by reducing turbulence and increasing velocity of the A/F mixture creating higher volumetric efficiency inside the combustion chamber (if done conservatively). Perhaps my post was misleading, you will never completely prevent carbon build up and you certainly don't *have* to remove the carbon during a rebuild. EXCESSIVE carbon can be bad and should be removed, but that does not fix the problem of why it got there (excessively) and further investigation should be perused. Smooth surfaces, in certain areas inside a cylinder head, can help reduce carbon build up. In other areas it may not. So we really kinda said some of the same stuff. To answer your question, I like what Dave said.
    For the sake of discussion, Jim, at what point does smoother become "not better"? Just curious if our answers are the same.

  4. #24
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    Mits, if you are only doing one head, and don't plan to be doing some number of them in the reasonably near future, your most cost-effective choice is to simply take the head to a reliable local automotive machine shop, which has a 'cold tank' chemical cleaning system for aluminium parts.

    There are, indeed, some good techniques mentioned above.....but what is your time worth, relative to the cost of sending the job to someone who has the setup to do it readily?

    (and do heed the warning about using any caustic cleaning material on aluminium......many years ago, a friend of mine, who was running an automotive machine shop, had just opened up one morning, and was in his office drinking his coffee and trying to wake up to face his working day....a friend of his came in and said.....'hey, Bob, may I put some parts in your hot tank?' Bob, somewhat absent-mindedly, replied 'sure, have at it'.....and then, just a minute later, remembered that his friend was working on a VW engine....Bob went running out into the shop, grabbed one of the wires running down into the tank, and lifted out a stud, with a little shred of the VW case adhering to it....the VW engine case halves, and the VW heads, were 'history' just that quickly)

    cheers

    Carla

  5. #25
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    looking around at a lot of people who "soup up" cars and engines ...
    i'd say the fat sods would gain more speed and acceleration ...if they went on a diet

    all the best.markj

  6. #26
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    looking around at a lot of people who "soup up" cars and engines ...
    i'd say the fat sods would gain more speed and acceleration ...if they went on a diet [Big Grin]

    all the best.markj
    BUT on oval track cars a driver who looks like Andre the giant all of his weight is on the inboard side of the car hehe, thats where you ADD weight if you must do so to meet a minimum weight class

    Bill

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    In a combustion chamber there is a boundary
    layer of gas that basically does not move during
    combustion. If the engine is experiencing
    detonation or pre-ignition then the boundary
    layer of gas gets blow through or swept away.
    This allows the combustion to come directly
    in contact with the aluminum and will scour
    it clean of carbon. It will also scour it clean
    of aluminum as well!

    The boundary layer serves to insulate the
    metal from energy that would otherwise be
    delivered directly from the hot gasses to
    the aluminum. The gasses are well in excess
    of the melting point of aluminum and will
    cause all kinds of problems.

    To my way of thinking the layer of carbon
    that forms in an chamber like that is a sign
    that your boundary layer is there, and doing
    its job.

    Really really clean scoured aluminum, especially
    at the piston crown, is a bad sign. It is
    often accompanied by teeny 'termite holes'
    which says, your piston is going away.

    Smoother walls do not always flow more gas.

    Jim

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    The old shade-tree tuner methods for squeezing HP out of motorcycles with a die grinder ceased to work well after about 1988 or so. Port profiles on downdraft configured engines became quite well evolved, and aside from matching the carb joints/spigots to the head, and blending the valve seat to the head casting, unless you had heads to spare and a flow bench, real gains were unlikely to be realized. As for port and combustion chamber finishes, I'd always leave intake ports with the finish that 220 grit abrasive rolls left; combustion chambers are bead blasted with glass, and exhaust ports get a once over with Cratex followed by Scotchbrite.

    Then it all goes in a hot water spray parts washer (or dish washer on "pots and pans").

    The crusty mineral-like deposits on valves scrapes off followed by a wire wheel. Do yourself a favor and tape over the stem where it runs in the guide. Don't touch those.

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    not sure if this applies to engines ...
    look into boats ...
    its been proofed time and again that smooth shiny hulls are slower than slightly rough ones.

    the reasoning behind me not polishing my ports and combustion chambers was ..
    1. I'm running on LPG ..so hardly any carbon .

    2. didn't have time .

    3....maybe... the rougher surface area provided more cooling area and mixing of the fuel.

    all the best.markj

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    How come golf balls have those dimples all over
    the outsides?

    Jim

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    Mr. Rozen,
    Keep your day job, Carbon does not form a protective layer, and well maintained properly running engine will have little or no carbon build up. Carbon is corrosive and causes pitting on valve seats and stem. Carbon is caused incomplete combsution.The carbon desposits will also sludge up the oil destroying the bearings.
    Golf balls,dimples cause turbulence.

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    Jim,cause it is easier than putting them on the inside.
    GW

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  14. #33
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    Turbulence very good.

    Why does this make the ball go farther and
    faster than if the ball were smooth?

    Could this principle apply to the inside
    of a combustion chamber?

    Jim

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    So why aren't airplanes dimpled like golf balls?

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    Because airplanes aren't shaped like
    spheres...

    http://www.aerospaceweb.org/question...cs/q0215.shtml

    Reynolds number....

    Jim

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    And oh, I forgot, and interesting discussion
    about why really smooth ports are not always
    a good idea - again, think reynolds number:

    http://www.tmossporting.com/tabid/3682/Default.aspx

    Jim

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    If you want to eliminate carbon, use water injection,for a feww hours before disassembly.
    The water turns to steam and cleans the combustion chamber.
    many folks don't know it, but IC aircraft engines used it, and it also allows a bigger spark advance.

    rich

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    Turbulence is good sometimes, it keeps the mixture atomized.
    On the turbo motors I do, I rough sand the ports after work to create a rougher surface to keep up the boundary layer turbulence otherwise you tend to get the fuel dropping out of suspension and puddling in the ports etc.

    You can buy soft material cup brushes specifically for cleaning out combustion chambers that are made of a soft material that doesn't damage the alloy and which take most of the elbow work out of the job...

    Also, if your not reboring/honing, then leave a ring of carbon around the outside of the piston crown, it helps the piston seal a little...

  20. #39
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    How about SeaFoam?

    Richard

  21. #40
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    Default cleaning aluminum

    "the best way to destroy something is to clean it improperly"

    i emphasize advice from above posts. example: aluminum wheel cleaner had been used a while for "really dirty wheel". it became linked with making aluminum brittle and wheels cracking (try googling it)

    water ? interesting. car pistons are are bright and clean if a head gasket leaks a little water in quench area. and i've been devising a plan to maybe do that at next oil change myself if i can be sure i can avoid hydro-lock (engine blows up).

    "parts washer" solvent, carburetor cleaner, kerosene, simple green, they are at local stores and good a other. and patience


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