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For many years now, HD has offered a popular set of
XL performance cams commonly referred to as SE 536's
(because they have .536" of lift). It's been a
popular grind because it's capable of making good
power and they're reasonably easy and inexpensive to
install. Although they need better than stock
springs and a check of piston-to-valve &
valve-to-valve clearance, unlike a lot of larger
grinds they don't need aftermarket lifters,
adjustable pushrods & collapsible covers, or roller
rockers, and that holds the costs way down. Also
they're not so large that cam box or tappet pin
clearancing is usually needed.
Shortly after the rubber mount Sportster was
introduced for the '04 model year, HD started
offering a new grind targeted at the new bikes. This
new cam set (NRHS part number 66-2519704) is known
as the "E" grind and is the same profile found in
all Buell XB models, except with a rotor cup keyway
and alignment marks set up for the XL cam box.
They're specified as "bolt-in" for the '04 and later
models, but can easily be fitted to any 91-03 as
well with a change of springs.
The "E" grind is intriguing because it offers a
little more lift than the SE536, .551" vs..536".
They also have less duration. On the intake side,
they open about the same place, but close 6 degrees
sooner at 44 degrees ABDC vs. 50 degrees for the
536's. On the exhaust side they're advanced 4
degrees on the open point and a full 20 degrees on
the close point. The latter really helps with the
exhaust TDC lift, which has always been something of
an issue when installing 536's.
So on paper, it's a grind that's narrower
and taller, with earlier timing to make power a
little lower in the rev range. The math and the
simulation programs all say to expect
more bottom end and mid range with a little
less on top.
Well, I ran a set in my personal S2 Buell for
awhile, and then I swapped'em out for a set of SE
536's with no other changes. And I always believe
the dyno more than the math:
Being an S2, this Buell has a regular Sportster
motor, not a Buell specific motor. Same heavy
flywheels. I've swapped out the stock hemi chamber
heads for a set of Stage 2 '04 XL1200 heads, and
fitted a decent exhaust (Buell race kit). CR is 10:1
and it still had it's CV40 carb at this time. So
it's representative a typical mildly modified XL
motor.
So as predicted, the 536's pulled away on top.
But contrary to the science, we got an absolute tie
through the bottom end and mid range. This is even
with heads
that flow very well at high lift, which should give
the additional lift and earlier timing of the "E"
cams an advantage down there. But it's not to be
found, the dyno doesn't lie.
Something the sheet doesn't show is that the
valvetrain is noticeably quieter with the SE .536's.
The "E" cams are getting a well deserved reputation
for creating a lot of valvetrain clatter, which was
actually my main motivation for swapping them out.
Getting more power on top with no loss anywhere else
was icing on the cake.
Both of these cam sets and many others are available
from NRHS. See our
camshafts page.
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