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Upgrading
an Exhaust System with Bill Johnston
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  A
stock exhaust system can get abused after many years of slamming it on the
rocks. The muffler on the left finally gave up it's life when the exhaust
hanger that was welded to it got ripped loose. You can also see how the
exhaust pipe on the right has been reshaped countless times. The original
restrictive exhaust was written off on this one. Time to replace it
too. |
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  Although
the new header came with a new exhaust gasket, the stock gasket was still
in great shape from a previous engine replacement, so it was retained.
Another good reason to use a stock gasket is the fact that it is larger,
thicker and has built in heat shields for the plug wire boots. The flange
on the Thorley is very thick, so we know it isn't going to be warping
anytime soon. Because of this thick flange, you need to make sure the
rear-most bolt (actually the only bolt - the rest are nuts) is long enough
to do the job. You need to make sure the bolt threads in at least 4
complete turns to make use of the full strength of the bolt. |
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 Once
the header is secured at the engine, the oxygen sensor needs to be
installed. Be careful as there is very limited room between the header and
the fender well. Also be sure to use anti-seize compound on the sensor
threads. This will make things easier when it has to be changed at a later
time. |
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  The
stock exhaust system has a spring loaded retaining clamp that allows
movement of the system when under stress. The flexible pipe on the left
was used to put that same capability into the new system. When selecting a
muffler, I wanted a low profile / low restriction unit but without being
abusively loud. The side by side tubes inside this unit will fit the bill. |
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  The
experts at Ernies Tire and Muffler concluded that a two inch exhaust
system would work well with the small engine and low restriction muffler.
There is enough back pressure to assure low end torque without being too
restrictive and limiting top end. |
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  Ever
try to change something under the vehicle and find that the exhaust system
is in the way? I had them put in an extra flange at the back of the
transfer case so I could drop the center section if I needed the elbow
room. The tip of the exhaust pipe was also routed out through the stock
location. The shape of the Samurai is such that if the fumes go straight
out the back, they curl back over the tailgate and into the passenger
cabin. |
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 Once
the exhaust was installed at a local shop, we took it out on the road for
a test run. The power increase was measurable. With the stock exhaust, the
0-60mph time was 42 seconds. With the new header and 2" exhaust it
only took 28 seconds. Still not a corvette, but a pretty impressive gain
for Zook! |
07/08/10 21:59
