| Performance and
Technical information on Stage 3 modifications to a Harley-Davidson 1340 Evolution
motorcycle engine. Building
the ultimate street bike engine
or
How to get 82HP from your 1340 Evolution engine.
 |
The camshaft in your bike has been upgraded. If
you have made these Stage 2 changes to your bike and are still looking for more power, you
may be ready for a Stage 3 engine where modifications can begin to get a little more
complicated. Better flowing heads and increased compression ratios are the way that this
is usually done.
There are many companies out there that are
competing for the dollars that Harley-Davidson owners are willing to spend on
their bikes. As an owner, you will be bombarded with a vast array of promises, claims and
inaccuracies in an effort to separate you from your money. Reading between the lines on
many of the performance claims can be bewildering.
Does the Harley-Davidson world need
another bolt together engine modification article? We decided it does, since the results
obtained by the engine upgrades listed here provided significantly better results than
those documented by the popular magazines aimed at the V-Twin crowd. The Motorcycle
Performance Guide staff continues to obtain better results than the "experts" in
the press.
How to build your own Stage Three engine
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This Stage Three engine did not involve any
internal changes to the engine other than replacing the OEM heads with the Screamin Eagle
1340 EVO heads. All modifications are made by bolt-on changes. Some special tools
and training is required to perform these modifications. Unless you are a very good
mechanic, it is recommended you find a competent shop to install the heads. For those of
you that want to install the heads yourself, Motorcycle Performance Guide recommends you
obtain the proper service manual for your bike.
Over the past several years we have installed and
tested many manufacturers components. The list of parts used in building the
ultimate 'bolt-on parts' engine is the end result of this testing. The best and least
expensive of the individual components was selected an tested as a single package. The
fact that virtually all the parts used for the project are from Harley-Davidson is a
coincidence. There was no plan or idea to use mostly Screamin' Eagle parts for this
project.
All the parts used are
readily available through your Harley-Davidson Dealer. The components were
installed and tested on a 1997 FXD Dyna Super Glide. No special tuning was performed to
achieve the results listed. All components were installed according to the manufacturer
instructions supplied.
 | Building your Stage 3 engine
Stage 1 improvements must be in place
Stage 2 improvements must be in place
Replace the OEM heads with the new Screamin Eagle Evolution heads
Change Oil and Filter
Install new spark plugs
Road test the bike
Dyno Tune the bike |
The results of the Dyno testing are excellent
as this bike's performance continues to improve. The test results showed the engine
producing 81.7 horsepower @ 5700 RPM and 87.1 ft. lbs. of torque @ 3900 RPM. The long,
flat power curve on this engine is ideal for street riding. There was an 18 horsepower
increase over the Stage 1 results and an 8 horsepower increase over the Stage 2 engine.
The engine is producing 28 horsepower more than a stock bike. Not bad for the relatively
investment in time and money required to get these results.
Just how fast is fast enough is a matter
of opinion. This 97 FXD was taken to the local drag strip in order to establish what sort
of 1/4 mile times could be turned with this bike. The bike proved to be a potent Harley
drag race bike by turning times in the 12:40 range with 105 MPH speeds. Considering the rider
for this test is relatively inexperienced, it is expected that in the hands of an
experienced racer, times in the 12:20 is quite possible.
The results are due to a well matched set of parts
being bolted-on to the engine. Seems that a little of that money the Dealers send back to
Milwaukee is going into engine performance research.
The ability to create similar results with
other manufacturers parts is a distinct possibility. Motorcycle Performance Guide chose to
work with parts that had proven ability to provide increased horsepower and torque. If you
use the parts listed in the "Ultimate Street Engine" series of articles, there
is little doubt in our minds that your can duplicate our results, provided the engine is
in good mechanical shape and properly tuned. Optional parts that have similar
specifications to the components used in our engine should provide very similar results. A
matched set of engine components, careful assembly and dyno tuning are the keys to
building a killer street engine. May your results be a successful as those we have
documented. |
