Technical information on Stage 3 modifications to a Harley-Davidson
TC95 motorcycle engine.
How to get 128HP from your Twin Cam engine.
You have decided that your current
engine isn't getting the job done. You have made Stage 2 changes to your bike and are still looking for more
power. Maybe your bolt-on Harley parts aren't getting you down the road as
quickly as you want? This this is the case, you are ready for a series Stage 3 engine.
Better flowing heads and increased compression ratios are the usual way to
break the 100 horsepower mark with your Twin Cam engine. Motorcycle Performance Guide is about
to blow the lid off this idea. We achieved 128 horsepower at the
rear wheels by using a carefully matched set of components and a lot of
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 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 and a select group of performance shops continue to obtain better results than the "experts" in
the press and what you can get by bolting on Harley-Davidson engine parts.
How to build your own Stage Three engine
This Stage Three engine requires internal changes to the engine.
Disassembly of the top end of the engine is required. Some special tools
and training is required to perform these upgrades. Unless you are a very good
mechanic and have access to a machine shop, it is recommended you find a competent shop to
perform these modifications. For those of
you that want to assemble the engine 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
this engine is the end result of this testing. The best and least
expensive of the components were selected and tested as a single package.
The horsepower your bike produces may vary from the results produced here.
If you use different parts or do not properly tune your engine, power may
change significantly. Motorcycle Performance Guide assures you that the
parts list and results are presented as accurately as possible.
The parts used
in this engine are available through CycleRama (727-546-0889), after-market parts companies
and your Harley-Davidson Dealer. The components were
installed and tested in CycleRama's shop. Dyno tuning is required to
achieve the results listed. All components were installed according to the manufacturer
|Building your Stage 3 engine|
Drain gasoline from tank
Remove gas tank
Disassemble the engine top end
Remove heads, cylinders and pistons
Remove cams, lifters and lifter blocks
Remove stock clutch
Swap stock heads for a set of CycleRama CNC ported heads
Send cylinders to machine shop to fit new pistons
Install cylinders with new pistons
Install upgraded cylinder heads
Install new cams
Install ignition module
Install lifter blocks with new lifters
Install adjustable pushrods
Install intake manifold and carburetor
Install new clutch
Install exhaust system
Change engine oil and filter
Change transmission oil
Add primary chaincase oil
Install new spark plugs
Set static ignition timing
Road test the bike
Dyno Tune the bike
Enjoy the ride
The results of the Dyno testing were excellent. The test results showed the engine
producing 128 horsepower @ 6600 RPM and 118 ft. lbs. of torque @ 4300 RPM. The power curve on this engine
is suitable for street riding. It
produces over 100 ft.lbs. of torque from 3200 to 6600 RPMs. That is some
serious power to the rear wheels.
This engine is producing 60 horsepower more than a stock
Twin Cam engine. Not bad for the relatively low investment in time and money required to get these results.
The results are due to a well matched set of parts
being installed in the engine. This is an engine combination that many
Harley shops do not want you to know about. Who would believe a TC95 could make over
The heart of this upgrade is a set of
CycleRama (727-546-0889) CNC Ported heads. The folks at CycleRama spent a
lot of time optimizing the ports on the Twin Cam heads before committing
to the current design. These heads will increase the power of your engine
The performance of the CycleRama designed
cam is matched to the flow characteristics of the cylinder heads. This cam
produced a wide power band.
The Thunderheader exhaust system was an important component in creating this high
horsepower. 2-1 exhaust systems are known for their strong mid-range power
and the Thunderheader did not disappoint us.
Other components used in this engine
|Screamin Eagle 44mm CV carburetor.|
|Screamin Eagle Pistons.|
|A performance clutch like the Barnett
Scorpion is required to control this much power.|
The ability to create similar results with
other manufacturers parts is a distinct possibility. Motorcycle Performance Guide
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