Stage Three Engine Design
The Stage Three Basic engine represents a more extensive
approach to improve engine performance with bolt-on components and a bolt-in camshaft.
Most people can perform these modifications themselves. Modifications over stock engine
are underlined in the list below. The estimated cost for these modifications ranges from
$1500 to $1800. The performance of this type of engine provides dramatic improvements over
a stock engine. An increases of 30 HP and 20 Ft.Lbs of torque was seen over the stock
Development of this engine has been a carefully documented series of changes with
the specific intent of creating a Stage Three engine that anyone with reasonably good
mechanical skills could do over a weekend. The 82 horsepower obtained by bolting this
engine combination together created an excellent perfoming bike.
In moving this bike from a Stage Two engine to a Stage Three engine, a set of
Screamin Eagle Evolution heads were added.
The major changes in making a Stage Two Basic engine over the Stage One Advanced is
the addition of an Andrews EV-46 camshaft. The original cam bearing was removed and
replaced with a Torrington. The stock Harley-Davidson push rods were used.
Prior testing with the Screamin Eagle 6000 RPM street ignition module had already
produced excellent. No reason was seen to change from the SE ingition module. A maximum of
73.9 HP occured at 5950 RPMs, with maximum torque of 78.1 ft. lbs. at 4100 RPMs.
The HP and torque curves for this engine combination was very smooth, with a broad torque
curve over 70 ft. lbs. starting at 2500 RPMs and extending to 5400 RPMs.
Assembly: Stephen Mullen
Crankshaft and Flywheel: H-D
Heads: Screamin Eagle
Intake Valves: 1.90"
Exhaust Valves: 1.62"
Valve Springs: H-D
Compression Ratio: 9.5:1
Pistons: H-D Stock
Cam: Andrew EV-46
Carb: Stock Keihin CV with DynoJet recalibration kit installed
Carb Jetting Information: 175 main jet, 45 slow jet installed
needle clip in highest position
Carb Idle mixture screw: CCP
Air Cleaner: Screamin Eagle K&N
Ignition: Screamin Eagle 6000 RPM street module
Ignition Timing: 34° BTDC
Coil: Screamin Eagle Dual Fire
Plug Wires: Magnecor 8.5mm
Pipes: Stock headers with HD Slip-on Baloney cuts
Gaskets: James Gaskets
Dyno Tuning Facilities: CycleRama, Pinellas
Park, FL. (813) 546-0889