The Harley-Davidson Blockhead Engine Harley-Davidson Motorcycles for Sales Our design or yours, we build 'em!
The Evolution Era
The Twin Cam Era
V2 EVOLUTION * 1984 - PRESENT Lots of bikers of all types everywhere feel to this day the Evo has
everything they hoped for since its introduction, 18 years after the Shovelhead. Differences include: - the Blockhead engine is 20 lbs. (9 kgs)
lighter
- has 10% more horsepower
- puts out 15% more torque
The Evolution engine kept the same 80 cubic inch classic dimensions
- it is actually 81.8 cubic inches (1,340 cc). It uses a bottom end from the Shovelhead alternator type with improved con-rods and a new alloy top end. Harley-Davidson has been very successful in improving
oil tightness and overall reliability and decreasing maintenance. The
changes responsible for achieving 70 bhp at 5,000 rpm: - steeper,
straighter ports for the new combustion chambers
- a
new ignition
- revised valve timing
- higher compression ratios
- redesigned lubrication system
The Harley-Davidson Evolution engine, or Evo, is sometimes
also called the Blockhead. It is an air-cooled,
45 degree V-Twin motorcycle engine manufactured by the Harley-Davidson Motor Company since 1984, with an 82 cubic inch (1,340 cc) displacement,
replacing the "obsolete" Shovelhead engine, until 1999 when it was replaced by the Twin-Cam 88. Most analysts consider the Evolution to be the engine that
saved Harley-Davidson from certain bankruptcy. Harley-Davidson's
official name for the engine was likely related to its reformed image following the 1981 employee-led buy back from AMF. The name Blockhead came from the tradition of nick-naming their engines
based on the rocker cover or box shape, which on the Evolution are clearly rectangular.
Though a major design advance for Harley-Davidson in many
ways, the Evolution is most distinct from earlier Harley-Davidson engine designs by virtue of its reliability, oil tightness,
and ability to run hard under all kinds of circumstances for tens of thousands of miles farther than any of its predecessors.
Both the heads and the cylinders of the Evolution
engine are made from aluminum, which is both lighter than iron (reducing overall vehicle weight) and a superior thermal conductor
to iron (improving air cooling efficiency). A problem is thereby avoided which occurs when the heads and cylinders
are of different materials. They expand
and contract at different rates which induces a relative motion; this motion ruins the gasket seal and necessitates replacement.
The blocky rocker boxes, aluminum heads and
cylinders (jugs) are the only part of the Evolution engine that can be said to be essential.
Probably the least striking engine in the lineup would be
the Evolution V-Twin. Nicknamed the Blockhead, the Evo is used in the current generation since its induction
in 1984. The Evolution is appropriately named, since it makes Harley-Davidson's
effort to maximize the design of it's 45 degree V-Twin for power, longevity and the absence of oil leaks and constant maintenance that had been virtually a given for Harleys. Maintenance has been greatly reduced, but expensive if you do it at the dealer, and if you do it yourself,
you need knowledge and specialty tools.
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