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    Wise Words

    LacrOne
    LacrOne
    graff king

    Number of posts : 484
    Age : 37
    Location : Naaarich
    aka : the king of the pencil
    Registration date : 2007-02-18

    Wise Words Empty Wise Words

    Post by LacrOne on Mon Jul 26, 2010 12:06 am

    This is a short article from the late, great mark herbert reference engine building,
    courtesy of the callook forums;


    I
    think building a large displacement VW engine has almost become an art
    form. Bore, stroke, rod length, and compression can all be combined in
    so many different ways that once you throw in the human factor you will
    usually end up with a different and unique motor every time.

    I
    know when I build a new motor that Iím always thinking for a new angle.
    With so many heads, carburetors, exhaust sizes and cams available you
    can choose your ďstate of tuneĒ or the RPM range that the motor will
    operate at. Other engine marks donít have this flexibility. Even the
    famous smallblock Chevy that also has an entire aftermarket industry
    behind it falls short of the aircooled VW in parts choice sometimes. So
    many parts choices are a great thing but of coarse it can be confusing
    sometimes.

    The best thing I can tell you is look, listen and
    learn. Sooner or later you will start to figure out who knows what they
    are talking about and whose parts work the best. For those of you who
    donít want to wait that long I will list some proven motor combinations
    later in this article.

    There are basically two kinds of people
    that want to build a more powerful VW motor. There is the person who
    wants the fastest thing they can build and there is the person who
    wants a reliable everlasting motor. I will try to bring these people a
    little closer together. First of all the main goal is more power. So if
    youíre going to build a more powerful motor thereís no sense in not
    going far enough. It costs about the same amount of money to build an
    1800cc stroker motor as a 2275cc stroker motor. And they will both last
    if they are assembled correctly. With the same carbs, heads and exhaust
    they will basically make the same horsepower but the 2275 motor will
    make it at a lower RPM and be much more fun to drive. Also a motor that
    turns 6000 RPM will out last a motor that turns 8000 RPM all the time.
    So the point is bigger is better when done correctly.

    There are
    some basic levels of performance with a VW engine. Things like heater
    boxes, boring and stroking determine how much performance you can
    obtain at a certain level. The first decision you need to make is do
    you really need your heater boxes? Are you going to be driving in cold
    climate for long periods of time? I did, and it sucked with no heater
    but at least my car was fast! :-) I eventually built an oil-cooled
    heater and all was fine. But donít kid yourself, it took me a long time
    to build a custom heater and I froze my butt off until then. If you
    choose to run heater boxes then I donít recommend stroking your motor
    or running it at sustained high speeds. The boxes are very restrictive
    and cause heat to build up in the heads and will eventually crack them,
    in some cases severely. Even a stock motor with cleaned up exhaust
    ports and a competition header instead of heater boxes will run cooler
    under extreme conditions.

    The next step is boring the case for
    bigger pistons. If youíre going to bore your case for 88s then why not
    bore it for 94s? It costs the same amount. Just remember that you must
    adjust your compression ratio as the motor gets bigger. If you just
    slap stock heads on a 1900 it will have 9to1 compression and thatís too
    much. I ran a 94◊69(1914cc) 7to1 compr. with Kadrons in my bus for
    years and it was a great motor as well as simple to build. Whether or
    not you can go to the larger 94 pistons depends what year case you are
    using. I donít recommend using 94s with the early 10mm head stud cases.
    The later cases as well as all new cases come with 8mm head studs and
    can be bored for 94s safely. While Iím talking about head studs I use
    chromoly 8mm head studs on all my motors. They can easily be torqued to
    25lbs or more and do not come loose. The stock 8mm studs can be used
    but they will only torque to 18lbs. and if you are buying after market
    8mm studs they are usually substandard so just pay a little more and
    get the chromoly ones. If your case comes with 10mm studs, the stock
    ones are fine.

    As far as big bore pistons are concerned the only
    ones that need help are 92s. If you have a 10mm stud case, these are
    the biggest pistons I would use. The tops of 92 cylinders are too thin
    so if you want to use them I would have them sleeved up to 94 bore
    size. A good VW machine shop will know how to do this. I will also
    sleeve 94s up sometimes because it gives a better seating surface in
    the head. When boring a case for larger cylinders its best to have it
    cut for wide base cylinder shims. This also gives a better seating
    surface. Sleeving the cylinder and using wide base shims keeps the
    cylinder from eating into the case or head. Iíve taken apart daily
    driver 2332 size motors after years of service and the heads were still
    torqued to 30 lbs.

    Next is stroke. The way I see it if your
    going to stroke it then STROKE it! Buy at least a 78mm crank and I
    prefer an 82. An 84 and larger crank should really have longer rods so
    Ill get to that in a minute. A 74mm crank is better than a 69mm and if
    you get one for free I would think about using it. The thing is if
    youíre buying a crank it only costs a small amount more for an 82. An
    82 crank with stock VW rods is an awesome combo! An 82 stroke with any
    bore and some OK flowing heads will smoke the tires as far as you want!
    It will also pull a bus and a trailer up any hill. The 82 crank
    combined with a stock length rod creates a shorter rod ratio than a
    stock 69 crank with the same rods. This short rod ratio causes the
    piston to snap harder at top dead center and in turn makes the heads
    breath harder. In short what you get is a high torque motor that pulls
    hard and has excellent throttle response. This combination coupled with
    some big pistons and a good set of heads and a medium size cam will
    make a great street motor or even an excellent bus motor. If you go
    with a big cam and heads you will have a real screamer capable of
    quarter mile passes in the 12s The key to this whole combination
    though, is a properly ported set of heads and the short rod ratio.

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