Here is some information on how to choose a a Cam. The # that dictates where power is made is the intake closing number. This is direct from the Mikuni North America website.
Cam Basics:
Correct cam selection is the single
most difficult choice facing the performance enthusiast. And,
unfortunately, we get it wrong about as often as we get it right.
An incorrect cam choice can result in decreased real-world performance
if the selected cam's operating range is not matched to riding
style.
The operating range of any Harley engine is determined by a number
of factors and the cam design is one of the most influential.
If the cam design is not matched to the other components and
is not matched to the desired engine power band (rpm range),
then the engine's performance will be disappointing. No amount
of carburetor tuning can compensate for having the wrong cam.
To get the "right" cam design, you need to do two things:
First, decide upon the rpm range you want to improve. Secondly,
use the list provided below and cam catalogues to select a cam
design that begins to work at the lower rpm of the power range
you have chosen. You'll probably be surprised to learn how few
of the available cam designs fit your expectations. However,
the list is accurate and if you follow its implied advice, you
will get an engine that performs as you wish it to.
Cam timing: what matters
The most important cam timing event is the intake valve closing
angle. The intake closing point determines the minimum rpm at
which the engine begins to do its best work. The later the intake
valves close, the higher the rpm must be before the engine gets
"on the cam."
Long duration, late closing cam designs are necessary to drag
the last bit of power out of an engine. Unfortunately, these
same cams can perform poorly under more normal riding conditions.
In the quest for maximum power output, many-too-many Harley owners
choose a late closing, high-rpm cam for their engine. The problem
with such choices is that the engine seldom spends time in the
rpm range favored by such cams.
The majority of virtually any Harley motor's life is spent in
the mid-portion of its rpm limits, between 2000 and 4000 rpm.
At open-road cruising speeds, that range is more like 2500 to
3500 rpm. With current Big Twin gearing, top gear at 2500 rpm
returns a road speed of 55 mph and 3500 delivers 84 mph. Riders
sometimes "putt" around at 2000 or less. Even when
accelerating to cruising speed, few of us use more than 4000
- 4500 rpm as a shift point. Very seldom, in day-to-day use,
do our engines get near 5000 rpm, let alone 6000.
Even the mildest of Harley-Davidson's aftermarket cams (Evo or
Twin Cam) do their best work above 3000 rpm. At 2000, the majority
of these cams seldom perform significantly better than stock
cam(s).
The rpm at which a Big Twin gets "happy" can be predicted
by the closing point (angle) of the intake valves. The angle
is expressed as the number of degrees After Bottom Dead Center
(ABDC) that the valves reach .053" from being fully seated.
The following list predicts the rpm at which the engine gets
"on the cam" based on the closing angle of the intake
valves. These relationships are approximate but should hold true
to within 200 rpm or so. They also assume that all other tuning
factors, exhaust, ignition, etc., are operating correctly.
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30 degrees = 2400 rpm
35 degrees = 3000 rpm
40 degrees = 3600 rpm
45 degrees = 4000 rpm
50+ degrees = 4500 rpm
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If you have one of the late closing
cam designs installed, say one that closes the intake valves
later than 40 degrees, then you cannot expect excellent performance
at 2000 rpm. No carburetor adjustment, ignition adjustment or
exhaust system can change this.