Are your Evo Big Twin, Pan or Shovel’s valves noisy even
after the engine is warmed up? If the answer is yes, they’re sending
you a signal. That clattering sound is the sound of lost power.
High bleed-down reduces volumetric
efficiency, the ratio between actual and theoretical flow of air
through your engine’s combustion chambers. That’s what determines
how well your engine “breathes,” and in some cases, whether it lives
A very important fact about volumetric
efficiency is found in the difference between solid and hydraulic
Because they’re air cooled, Harley
engines “grow” with increasing temperature. A solid-lifter
street-ridden Harleys on pump gas will grow as much as .060"
between the camshaft and the rocker shaft at 350-degree head
Now take that .060" and multiply it
by the rocker arm ratio, subtract that figure from the valve lift and
duration of the cam specifications and guess what, that solid lifter cam
just cost you approximately 18 percent in volumetric efficiency! Not to
mention the damage to the valve train components.
Hydraulic lifter bleed down rates are
still an unknown factor. However, bleed down rate is controlled by a
number of factors such as valve lift and duration of your cam, valve
spring pressure, and oil temperature and viscosity.
If your hydraulic lifters are noisy after
warm up you can safely say the bleed down rate is costing a lot of
After much time and testing and
development, FLO Headworks is proud to make available the High
Performance Hydraulic Lifter Kit that will fits Harley-Davidson big
twins from 1948 on.
This top-quality kit is also compatible with
most aftermarket cams and stroker motors. Available clearance will
accommodate cams up to .600 lift and valve spring pressure in excess of
400 pounds open.
For 1948 to 1953 models, the case must be
drilled for oil passage. The lifter hydraulic unit has been greatly
improved with anti-float, anti-pump-up and anti-bleed-down features.
High tech bypass and check systems will
maintain totally silent operation in a variety of adverse conditions.
Oil pressure requirements start as low as 10 psi and go all the way up
to 50 psi. Oil viscosity from 20/50W up to 70W, with air temperatures in
excess of 100 degrees. The lifter dimensions have been increased in
three critical areas.
The body diameter is .110 thousandths
larger. The body length is .195 thousandths longer. The roller diameter
is .088 thousandths larger. The lifter blocks are cast with 356 grade
aluminum alloy. Hardened for maximum strength and durability. Detailed
and polished to give a show clean appearance.
The pushrods are manufactured by FLO
seamless chrome moly tubing, centerless ground for precision
construction. The tips are welded and hardened. The nuts are made of
1018 steel with 5/16 by 32 NEF threads for maximum strength and
FLO Headworks High Performance Hydraulic
Lifter Kit comes complete with gaskets, installation instructions and
all necessary hardware (not pictured).
Our work and products are guaranteed for
one year. For an estimate on your particular application contact us
directly by telephone at 805-481-6300 or you can