MATERIALS:
All Del West valves and keepers
are completely CNC machined and precision ground from domestically traceable
MIL-spec Ti-6242 vacuum arc triple melt titanium. The lower mass of Del West
titanium valves (approximately 40% compared to steel), combined with our
matching titanium locks, allows the use of more
aggressive cam profiles without loss of valve control. In turn, this provides
broader torque curves with higher peak rpm and greater power.
All Del West Moto retainer are now produced in Plasma Nitride – Steel.
DESIGN:
All critical dimensions of the parts
are controlled 100% for dimensional accuracy to the most demanding specifications
and for surface Finish
PROCESSING:
Precision Machined/one piece
forged. Final machining is still done in the way and
to the exacting standards that established the Del West reputation for
superiority. Forging allows us to provide full CrN-coated
valves at the same prices as our previous Moly-coated, machined-from-solid
valves.
COATING:
CrN (Chromium Nitride) coated –
ultimate protection against seat erosion, tip wear, seat and stem erosion.
Chromium Nitride is an extremely hard, inert, thin film coating that is applied primarily to precision metal parts. Chrome
Nitride (CrN) offers greater temperature resistance
than TiN and is an ideal choice in high temperature
environments. CrN also performs well in corrosive
environments and in sliding wear applications.
A two-year period of track
testing on paved and dirt tracks with the country’s leading engine builders
proved that fully coating our valves with Chromium-Nitride lowered racer costs
by significantly extending valve life, while maintaining the level of
performance Del West customers have always expected. Here’s
what Del West’s conversion to fully-coated forged titanium valves mean for you:
·
Chromium-Nitride is a
thin yet extremely durable, low-friction coating, applied by plasma
vapor-deposition to seats and stems.
·
It has been
competition-proved to reduce rebuild frequency
·
There’s no cost
premium for a superior product
·
Dimensional accuracy
is to the same exacting standards that has always made
Del West the valve of choice for leading engine builders from MotoGP to NASCAR and Formula 1
·
Still back-cut, ready
to install without machining, and no undercut
·
Durability and
performance proved
BENEFITS OF DEL WEST VALTRAIN COMPONENTS:
RIGIDITY:
The most
common cause of valve float is a lack of rigidity in the valve train. Rigidity
is the ability of a structure to maintain a constant distance between two
points under load, and is critical in three aspects.
The are several point of
contact in the valve train that need to maintain rigidity despite transmitting
the motion.
Only if the
distances between those points remains constant and the valve stem itself does
not flex will the actual valve timing match the timing designed into the cam
lobes. More simply put, when the rocker arm or valve stem flexes, valve timing can be dictated as much by the flex as it is by the cam
design.
Even without
encountering valve float, if either the valve stem or the rocker arm flex,
valve lift will be reduced.
Reduced valve
lift results in less filling of the cylinder and reduced cylinder pressure, and
cylinder pressure is directly proportional to horsepower. The negative effect
of flexing rocker arms increases with rpm.
MINIMIZE VALVE FLOAT:
One of the most important
considerations in selecting valve train components is to keep the valves
accurately producing the timing designed into the cam profile.
At higher rpms, failure to follow
the cam profile results in valve float or bounce, in which the valve rebounds
of the seat one or more times after initially closing.
Valve float allows cylinder
pressure to ‘leak’ past the valve at each bounce. This reduces cylinder
pressure, which in turn reduces power. Intake valve bounce causes pressure
waves to low back up the intake tract, and in some cases can lead to valve
failure.
Lighter valve train components,
including titanium valves, tend to minimize valve bounce.
REDUCED VIBRATION:
In addition to
the operating frequency, valve train components have what are
called natural frequencies, or harmonics.
A harmonic is defined as a narrow range of RPM where the amplitude or
size of the vibration goes through a maximum or becomes very large. On either side
of this vibration peak the size of the vibration is
quite small.
As rpm
increases, valve train components can experience one or more harmonics.
The greater the RPM range of
engine operation, the greater the number of harmonic vibrations that will
occur. If all the parts except the spring are rigid, the shape of the cam lobe
determines the rate and speed at which the valve opens and closes.
How often the cycle is repeated in a given time period is determined by the rpm.
Harmonics can occur at different points across the engine’s operating range,
and can cause loss of valve control at surprisingly low rpm.
It is not
unusual to see a power curve with a dip in the middle, this “McDonald’s
arches” effect being caused by harmonic spring vibration. To reduce, if not
eliminate this harmonic problem, the parts need to be
selected to work together, as part of a system.
It is even possible for different
natural frequencies in the various valve train components to allow one part in
the system to act as a damper for another, just as a shock absorber dampens the
oscillations of a suspension spring. How can valve train
components be made to work in harmony? Lacking very expensive testing
equipment such as Del West employs, that is accomplished
by following the basics of smart engine building.
REDUCED MASS:
One of the
first things to look at is the combined mass (weight) of the valves, retainers
and locks. Replacing steel valves with titanium gives a reduction in mass of
approximately 40 percent.
The same
reduction is achieved with titanium retainers and
locks. Reducing the mass allows higher rpm and a broader torque curve, and it also reduces the loads on valve seats, springs and the
camshaft, increasing engine durability. Reducing mass also shifts harmonics to higher
RPM.