AUGUST 2020 | ENGINEBUILDERmag.com 41
you have to decide whether you’re
going to run a tight tulip, a wide
tulip, an undercut, a radius margin,
etc. – there’s so many things to look
at. ese decisions are also dependent
on what type of combustion chamber
you’re working with as well.”
On exhaust valves, you have
what’s called a margin, which is
basically where the valve seat angle
meets the outside diameter of the
valve face. On the bottom side of
that, which is actually exposed to the
combustion chamber, some valves
have a 90-degree edge and others have
a radius edge.
“What we have found throughout
the years is if you can form a radius
on the end of the valve, air ow will
get around the valve a lot faster,” he
says. “ at will also help with spool
if you’re running a turbocharger, and
it will also allow exhaust gas velocity
to increase around the valley for
instances like a nitrous application.”
Taking a look at diesel valves,
Alderson says he typically utilizes
Inconel intake and exhaust valves or
Inconel exhaust and stainless intake
valves.
“With a lot of the Powerstroke
stu , we’re working with a very small
bore size, so you’re fairly limited
on valve size without going to a
considerably larger bore,” Alderson
says. “We try to o er drop-in options
that don’t require reinventing the
wheel. We can do a stellite facing
valve or a full stainless valve. We’ve
done di erent one-piece valves
and we’ve done di erent two and
three-piece valves. It depends on the
application.
“A lot of the factory valves only
have a ash chrome plating, so we
do a bit of a deeper chrome plating
to them, which helps for wear and
resistance. For something that’s going
to run higher boost or get taken
to the track occasionally, we like astainless, nitrided option.
If it’s an all-out, maximum
e ort, competition engine,
we go with Inconel.”Rocker Arms
In many engine builds,
strict attention is not
paid to rocker arms.
ey are not thought of
as contributing to the
durability, longevity,
consistency, and power
of a race engine. But top
engine builders hold the
opposite to be true or they wouldn’t
be where they are.
“Many believe the ‘lowly’ rocker
arm is just a lever to transfer motion
from one direction to another,”
says Phil Elliott of T&D Machine
Products. “But a fully quali ed
engine builder who designs an engine
for a speci c application knows the
contribution that proper rocker arms
make to the overall combination. Due
to engine builder preference, and that
T&D is exible in manufacturing,
most of our rocker arms are custom
built.”
Getting the camshaft’s full lift/
duration to the valves, means proper
installation and setting of the rocker
arms is an important facet to reaping
100% of available power.
“High-stress applications
demand a somewhat di erent rocker
arm,” Elliott says. “For example,
supercharged or nitrous applications
may require a steel rocker body. at
can also apply to o -road, boat and
oval track racing. It removes ex from
the valvetrain, while adding longevity.
Many applications don’t require going
that route, but if your application will
operate in those high-stress arenas, or
if cylinder pressure is going to be very
high, steel rocker bodies will be an
asset to the combination.”
In fact, just about the entiremarket over the last seven to 10
years has shifted to steel rockers, but
aluminum rockers are also still widely
used.
“We always were a fan of
the aluminum rocker, but the
applications are constantly warranting
something better,” McDonald says.
“Aluminum rockers are still our
biggest seller, however, the industry is
shifting toward steel rockers. All the
high-end motors – Pro Stock, Sprint
Cars, Pro Mod – are pretty much all
steel rockers now. You can’t beat the
longevity of a steel rocker. e steel
rocker has really found its place.”
While steel is the go-to material
these days, there are many di erent
styles of rockers for engine builders to
choose from.
“ ere’s still a lot of people that
run stud rockers,” he says. “However,
certain applications will warrant
getting rid of stud rockers for shaft
rockers because studs can’t handle
the stability, high rpms and the
spring pressure. You’re going to need
something more rigid and something
that can locate and lock down a lot
better like a shaft rocker. A shaft
rocker holds its lash a lot better than a
stud rocker ever could. A shaft rocker
also gets rid of all those guide plates,
poly locks and girdles to keep the stud
rocker stable.”40-43 eb.aug20 Valvetrain.indd 41 8/7/20 8:32 AM
Naresh Jariwala