tech
torque
CHOOSE THE PERFECT CAMSHAFT
WITH SUMMIT RACING’S NEW CAM TIMING CALCULATOR
Choosing the right camshaft can
be an exercise in frustration, even
for seasoned racers and engine
builders.
With so many choices available, it’s not simply a
matter of picking a cam based on lift and duration
numbers – you need a good understanding of the
four individual valve events and their effects on
performance.
Summit Racing has created a new tool that can
help eliminate the uncertainty of choosing the
right cam for your engine.
Developed with help from the experts at Cam
Motion, the new Summit Racing Cam Timing
Calculator is a powerful tool that lets you input
and manipulate valve timing specifications to
determine the ideal camshaft grind for your
engine. But first, a little lesson on valve timing
events:
Camshaft Selection
There are four valve timing events
that determine camshaft duration,
lobe separation, and advance. It’s
important to understand what they
are and how they affect engine
performance. The valve timing events
in order of importance are:
Intake Valve Closing (IVC)
This event has the most control over
the engine’s powerband. For example,
closing the intake valve later after
Bottom Dead Center (BDC) trades low-
end torque for high-end horsepower.
Intake Valve Opening (IVO)
This is the most important event for
idle quality. The idle gets rougher
when we open the valve earlier
(Before Top Dead Center/BTDC), but
gain more airflow on the intake
stroke.
Exhaust Valve Closing (EVC)
This determines the compromise
between reversion at low RPM and
part throttle and the positive effects
of scavenging higher in the power
band and at wide open throttle.
Exhaust Valve Opening (EVO)
Cam Timing Events for
This is the least critical of the four
events due to high residual cylinder
pressure blasting out of the cylinder
even before the piston hits Bottom
Dead Center. EVO helps rid the
cylinder of burnt gasses, but it’s a
compromise. Opening the exhaust
valve too early decreases pressure on
the piston that could be used to turn
the crank, but it does reduce pumping
losses (pressure working against the
piston when it’s on the upstroke after
BDC).
For a more in-depth explanation on
valve timing, click here for a Summit
Tech Talk video on Summit Racing’s
YouTube channel and also check out
the below links for relevant stories on
Summit Racing’s OnAllCylinders blog:
• Comparing Camshafts Part 1
• Comparing Camshafts Part 2
How the Cam Timing
Calculator Works
Now that you have a better
understanding of valve timing how it
affects performance, you can use the
Summit Racing Cam Timing Calculator
to convert camshaft duration, lobe
separation, and advance into the four
valve timing events.
You can also tweak any of the cam
specifications to see how the changes
affect the cam profile. Armed with
this information, you can quickly find
the right cam for your engine, and
also compare different cam grinds
to see how each one affects engine
performance.
This Summit Racing Tech Talk video
available by clicking here shows
the Summit Racing Cam Timing
Calculator in action. Once you have
a good handle on how it works, visit
SummitRacing.com to find the
calculator (click here to view) and
create your perfect camshaft!