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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><a
href="http://www.enginebuildermag.com.php53-8.ord1-1.websitetestlink.com/2013/11/maintaining-your-balance-engine-building-tips-to-reduce-nvh-and-increase-life/?utm_source=EB+Newsletter+-+Subscribers&utm_campaign=1656b77ca3-enginebuilder+newsletter&utm_medium=email&utm_term=0_6ca466f60c-1656b77ca3-83595957##"></a><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>A high revving racing engine obviously needs a good balance to minimize
these destructive forces, but balancing can be just as beneficial to low
revving engines, too.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Nobody would argue with the fact that engine balancing is right up
there with “blueprinting” an engine. The goal is to equalize the
reciprocating and rotating forces inside the engine so it will run smoother,
last longer and achieve its maximum power potential.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Although balancing would seem to be most important for high revving
performance engines, it can also provide benefits for relatively stock engines,
as well as low revving heavy-duty diesel engines. When proper balance is
achieved, it reduces NVH (noise, vibration and harshness) that can be felt
inside the vehicle, whether it is a daily driver, a race car or over-the-road
truck.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Better balance makes for a smoother running and quieter engine. But,
even more importantly, proper balance also maximizes the engine’s
longevity by reducing the pounding that imbalance produces on the
crankshaft’s main bearings.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The centripetal forces generated by any imbalance increases
exponentially in proportion to speed. Double the rpms and you quadruple the
force. A 2 oz.-in. (ounce-inch) imbalance on a crankshaft will generate only
about 14 pounds of centripetal force at 2,000 rpm. But when the engine revs to
8,000 rpm, that slight imbalance now becomes a pounding force of 227 pounds!
The resulting thrashing motion that the crankshaft experiences with every
revolution can pound the bearings and main caps to death over time – and
the greater the imbalance, the greater the pounding force that is being exerted
on the bearings and main caps.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>When a crankshaft spins, it wants to rotate around its center of
gravity. That’s a basic law of physics. As long as the rotating weight is
evenly distributed around the circumference of the crank, the center of gravity
will line up with the center axis of the crank and the crank will spin smoothly
without any wobble.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Most racers today want their cranks balanced to within one ounce or
less, and many of the big boys (NASCAR, ProStock, etc.) will aim for fractions
of a gram<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>But, if there is an imbalance, it will offset the center of gravity and
force the crank to oscillate from its true axis as it spins.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
Of course, the crank can’t wobble too much because it is held in place by
the main bearings. Even so, the wobbling motion exerts a pounding force against
the bearings and can even cause flexing and bending within the crankshaft
itself if the forces are great enough.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Over time, this may lead to metal fatigue, stress cracks and crankshaft
failure. It can also create annoying engine vibrations that can be felt
throughout the<br>
vehicle, as well as harmonics in the camshaft and valvetrain that may result in
a loss of horsepower.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Whether you have a large imbalance force acting on the crankshaft over
a short period of time, or a relatively small imbalance force acting on the
crankshaft over a very long period of time, the end result can be the same in
either case: bearing fretting and fatigue that eventually leads to bearing
failure and/or crank failure.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>A high revving racing engine obviously needs a good balance to minimize
these destructive forces, but balancing can be just as beneficial to low
revving engines, too, including big over-the-road truck engines that only turn
1,800 to 2,800 rpm. Why? Because of the cumulative effect even a small
imbalance can have on engine longevity.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Recognizing this, the auto makers have tightened up their balance
tolerances in recent years to not only reduce NVH but to also extend engine
durability. What used to be “race only” balance tolerances are now
everyday production tolerances for many engines. Today’s lighter and
higher revving engines can’t handle as much imbalance as older, heavier
cast iron engines, so they are typically balanced to much closer tolerances.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Little Tolerance for Imbalance<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
The “old school” tolerances for balancing used to be plus or minus
2 ounces for stock engines (56 grams), half an ounce (0.5 oz. or 14 grams) for
street performance and two-tenths ounce (0.2 oz. or 5 to 6 grams) for racing engines.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>These numbers provided relatively good results with the engines and
speeds that were common a couple of decades ago, but they are not even in the
ballpark with today’s stock and racing requirements.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Most electronic balancing equipment that’s on the market today
can easily achieve balances to within 0.1 grams (0.004 oz.), or even less for
specialized applications such as turbocharger impellers that spin at extremely
high rpms.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>A dime weighs 2.268 grams (0.08 oz.). If you glued a dime to the
outside edge of a counterweight on a crankshaft, it might not cause much of an
imbalance in a low revving stock engine, but it would be too much of an
imbalance for most performance engines.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Most racers today want their cranks balanced to within one ounce or
less, and many of the big boys (NASCAR, ProStock, etc.) will aim for fractions
of a gram.<br>
On some of Ford’s newer V6 engines, the factory balance is within 0.16
oz.-in. (4.5 grams) – which is old school racing tolerances. It’s
important to keep this in mind because any time you are rebuilding a late model
engine or a performance engine and change internal parts (pistons, wrist pins,
rods or the crank), you change the balance.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The same thing happens with externally balanced engines if you replace
the flexplate, flywheel or harmonic dampener.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Some aftermarket replacement pistons and rods weigh about the same as
the original parts, but others may be heavier or lighter depending on their
design. What’s more, some piston and rod sets may be weight matched fairly
close (plus or minus 2 grams) from the factory while others vary quite a bit.
Consequently, if you do not weigh the parts on a highly accurate scale, you
have no way of knowing how much they actually weigh or how much their weight<br>
differs from the original parts.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Balancing has become a sought-after service in some segments you may
never have considered, and it remains an important profit center in many
machine shop operations.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The Bobweight Effect<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
All crankshafts have a target bobweight (plus or minus 2 percent typically)
that approximates the weights of the pistons and rods that are going on the
crank. The closer the target bobweight of the crank to the actual parts, the
less drilling it takes to bring the crank into balance. Because of this,
it’s important to know the approximate weights of the pistons and rods
when you are buying or ordering an aftermarket crankshaft.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Balancing Basics<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
One of the basic goals of engine balancing is to equalize the weights of the
pistons, wrist pins, rings, connecting rods, rod bolts and bearings so as to
equalize the reciprocating and rotating forces that are acting on the
crankshaft.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Each of the parts is carefully weighed to determine which piston and
which rod is the lightest. The other pistons and rods are then ground or
machined to equalize their weights to the lightest one in the set. Another
trick that some engine builders use is to mix and match heavy and light pistons
and rods that share the same journal to equalize the weights on each journal.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Once the weights have been measured and equalized, the rotating
and reciprocating weights need to be separate from each other. The rotating
weight is the big end of the<br>
connecting rod, rod bolts and rod bearings, plus a few extra grams for oil
while the reciprocating weight is the small end of the rod, wrist pin and
locks, piston and rings.<br>
After these values have been determined (for a 90-degree V8 engine), bobweights
that simulate 100 percent of the rotating weight (times 2 because there are two
pistons sharing the same journal) and 50 percent of the reciprocating weight
(times 2 for the two pistons also share the same journal) are assembled by
stacking metal weight shims. The bobweights are clamped on each rod journal and
the crankshaft is then spun on the balancer.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Highly sensitive motion sensors detect any wobble in the crank, and the
balancer’s electronics split the crankshaft into two halves (right and
left) and essentially balance each half of the crank separately (2-plane
balancing).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Some balancers also compare the results of the left and right sides to
see how the forces interact (3-plane balancing) before displaying the index
location and amount of imbalance that needs to be corrected. Weight is then
removed by drilling or machining the counterweights, or added by installing
heavy metal tungsten (“mallory”) plugs into the counterweights to
offset the indicated imbalance. The crank is then spun again to check the
corrections that were made. This procedure is repeated as many times as it
takes to achieve the desired degree of balance.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>A high revving racing engine obviously needs a good balance to minimize
these destructive forces, but balancing can be just as beneficial to low
revving engines, too.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>In the case of superlight racing cranks, the counterweights may be
turned down so much that there isn’t enough metal to offset the
bobweights. If this is the case, the crank will likely require heavy metal
plugs to balance it and/or external balancing with the flywheel and harmonic
dampener.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Another issue to watch out for is that some cheaply made import
crankshafts may not have enough metal in the counterweights to achieve balance
easily or inexpensively (heavy metal plugs are expensive). Or, the
counterweights may not be positioned correctly on the crankshaft to allow
proper balancing.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>There’s no way of knowing this until you start to balance the
crank and realize it’s way off the mark and will take a lot of work to
balance it.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>To reduce overall weight and cost, most crankshafts for 90-degree V8
engines have six counterweights instead of eight. No counterweights are used on
either side of the center main bearing. If the crank had eight counterweights
(one for each cylinder), each weight would be offset 180 degrees from its
journal.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>But with only six counterweights to serve this function, the
counterweights are offset 135 degrees from their journals.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Some math whiz figured this out and saved the auto makers a lot of
money – but also made life harder for anyone who is trying to balance a
really high revving engine or one with a long stroke crank.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>So racing cranks with eight counterweights are available for
applications where the extra weight really doesn’t hurt from a
performance standpoint, but really helps from a balance standpoint. NASCAR
engines typically run in excess of 9,000 rpm for much of a race so having an
eight counterweight crank helps control vibrations and harmonics at these
speeds.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The basics of balancing haven’t really changed over time –
add weight if it’s required, take it away if needed. What has changed is
the market’s expectations and the technology available to make balancing
an accessible service.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Weighing Your Options<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
When it comes to balancing “tricks” some performance engine
builders will slightly overbalance or underbalance the crankshaft in an attempt
to minimize vibrations and harmonics within a specific rpm range. Overbalance
means adding extra weight to the bobweights when the crank is balanced, while
underbalancing means using less weight on the bobweights when the crank is
balanced.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>For example, if you want to overbalance an engine 2 percent, you would
use 52 percent of the reciprocating weight of the pistons and small rod ends
instead of the usual 50 percent weight when assembling your bobweights. To
underbalance the engine 2 percent, you would use 48 percent of the
reciprocating weight instead of the usual 50 percent.<br>
Imbalances and harmonics in the crankshaft are transmitted to the camshaft and
valvetrain by the timing chain or timing gears.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>If a slight overbalance creates vibrations that offset any undesirable
valvetrain harmonics, the engine runs smoother and makes more power. But if the
vibrations don’t offset and amplify one another, things only get worse.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Some say that slightly overbalancing a high revving engine helps dampen
harmonics that may occur above a certain rpm. Those who use this technique
claim it makes an<br>
engine run smoother and makes more power. The problem is, overbalancing may or
may not smooth out high-rpm power and vibrations, and it may make things worse.<br>
Many piston and rod suppliers recommend a neutral balance (the usual 50 percent
of the reciprocating weight) unless an engine is really experiencing some
severe high-rpm shakes. What works on one engine may or may not work on another
engine because of differences in valvetrain geometry, stiffness and dynamics.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Those who swear overbalancing works typically recommend overbalancing 1
percent (using 51 percent of the reciprocating weight) if the engine revs above
8,000 rpm, 2 percent if it revs to 9,000 rpm, and 4 percent if it revs to
10,000 rpm.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>By comparison, some Formula 1 racing teams underbalance their engines
several percent because they have found it helps offset the second order
harmonics that occur at extremely high engine speeds (up to 18,000 rpm in some
of these engines!) Underbalancing is also being used in some monster drag
motors with long cranks (up to 4 percent underbalance) to smooth things out at
high-rpm.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The point here is that overbalancing or underbalancing essentially
creates a dynamic imbalance inside the engine. The imbalance will create vibrations
the same as if the engine had not been balanced correctly in the first place.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>But if the imbalance is tuned for a specific rpm range, it can offset
bad vibes that are hurting performance. What happens outside this rpm range in
a racing engine doesn’t matter because it’s outside the
engine’s normal power range.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Did You Know…<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
Engines that run at fairly constant high rpm typically benefit most from
overbalancing (or underbalancing in the case of Formula 1 engines). <br>
However, engines that have to operate across a wide range of rpms may or may
not realize any benefit from overbalancing or underbalancing, depending on the
dynamics inside the engine. It may help at some speeds and hurt at others.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>When it comes to balancing “tricks” some performance engine
builders will slightly overbalance or underbalance the crankshaft in an attempt
to minimize vibrations and harmonics within a specific rpm range.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>‘Ins’ and ‘Outs’ of Balancing<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
Many engines such as small block Chevys are internally balanced. The crankshaft
has enough mass in the counterweights to allow the rotating and reciprocating
forces to be balanced by machining the crank.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>The flywheel and clutch are neutral or zero balanced, which means
engine balance is unaffected if the flywheel or clutch have to be replaced
later.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Smallblock Fords, by comparison, are externally balanced, as are some
big block Chevys (454s).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>This means the flywheel (or flexplate) and harmonic balancer contribute
to overall engine balance and must be mounted on the crank when it is balanced
to achieve proper balance. It also means the index position of the flywheel (or
flexplate) on the crank must be maintained if it is removed and reinstalled so
balance isn’t upset.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>It also means engine balance will be lost if the flywheel (or
flexplate) is replaced with another unit unless the balance of the replacement
is perfectly matched to the original (which it may or may not be).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Most performance engine builders say the best way to go is to internally
balance the engine (if possible) for the advantages listed above.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Removing Stress<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
The harmonic dampener or balancer on the front of the crankshaft may be used to
externally balance the engine, but it’s main purpose is to dampen
torsional vibrations in the crankshaft.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Every firing pulse twists the crankshaft, so the dampener helps smooth
out the jolts to reduce stress on the crank. If the dampener fails to do its
job because it is defective or lacks sufficient mass, the crank may be stressed
to the point where the nose snaps off or it breaks.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Consider <st1:place w:st="on">Cam</st1:place> Balancing, Too<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
Many people overlook camshaft balance when balancing an engine because a
camshaft has a relatively small diameter (only a couple of inches) and it turns
at half the speed of the crank.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Even so, a slight imbalance in a camshaft can become a significant vibration
in a high revving engine – possibly enough to cause lifter bounce,
valvetrain harmonics and<br>
ignition timing issues with a cam-driven distributor.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>For this reason, many high-end racers are also balancing their
camshafts now, too.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Larry - <st1:City w:st="on"><st1:place w:st="on">Cleveland</st1:place></st1:City><o:p></o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
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12.0pt'><o:p> </o:p></span></font></p>
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12.0pt'><o:p> </o:p></span></font></p>
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