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The Pontiac CV-1 represents
a clean sheet redesign of the conventional Pontiac cylinder head. So unique are some of its features, they are
the subject of a patent filing.
Perhaps the most
obvious feature are the canted valves. The CV-1 canted design
is unlike other canted designs because the valve heads are horizontal in the chamber, not offset. This
feature, in combination with the large amount of valve roll, reduces the amount of valve to valve clearance
required, permitting the use of larger valves in the same bore size. The stock intake valve placement aligns
it with the stock cylinder scallop on most pontiac blocks for maximum low lift flow. The stock exhaust valve placement
allows for a longer, smoother port shape with a higher short turn radius in comparison with other canted offset designs. From
a performance perspective, these canted valve/port principles offer improved breathing over a typical inline valve
design, here's why:
As shown in figure 1, the valve
heads are tilted to the inside. As they open, their path projects them toward the middle of the cylinder. This
reduces the shrouding effect, which occurs when a large valve is too close to the cylinder wall. Reducing this effect permits
the use of larger valves with improved flow in the same bore size.
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The same principle applies to port alignment relative to cylinder.
Since the port is canted on the same axis as the valve, it causes the airflow to follow the valvestem path down
into the middle of the cylinder. The CV-1 layout has been designed with the maximum amount of valve and port cant angle possible
for optimum breathing with the traditional layout and bore spacing.
See figure 2
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Next, the intake tract was redesigned to eliminate restrictions.
Original Pontiac intake port size is effective for moderate performance applications. However, the stock siamese design
limits cross sectional area to an insufficient quantity for large displacement (>450ci) competition engines without
expensive custom valvetrain. The new Spread Port design allows an affordable way to increase port size (3.25"csa
as cast; 3.7"csa ported) for effective breathing. What makes it affordable is the ability to use "off the shelf" valvetrain
components for most large displacement performance applications. If supersize (>535ci) hi rpm breathing is needed, then 2.35-2.375" intake
valves can be installed. Additional porting can then easily achieve 4.25"csa with soon to be available rocker shaft systems
for those ultra high performance needs.
See figure 3
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Figure 3
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Illustrating the complete Spread Port layout, the intake ports are no longer siamesed. The CV-1
redesign has separated the intake ports so that they are now equally spaced. Since they retain symmetry, there are
no good and bad intake ports.
This relocation solves the age old Pontiac nemesis- the push rod bulge. The result
is a dramatic increase in port width (1.61" as cast) and efficiency due to constant cross sectional area.
See figure 4
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Figure 4
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The chamber has been updated with dual quench technology.
This efficient chamber is designed with opposing squish pads for uniform mixing. The increased turbulence enhances flame
front travel for better detonation resistance, allowing the use of higher compression ratios. Spark plug location is
centralized to equalize flame fronts for complete combustion, and reduce required ignition advance.
See figure 5.
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Figure 5
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The exhaust flange in as cast configuration is traditional Pontiac
Ram Air round port. The location of the flange has been raised about 1/2", but still compatible with most stock applications.
See figure 6
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The exhaust port is signature Pontiac, but with two distinct improvements.
First, the stock valve angle has been reduced dramatically to
straighten the port and add height to the short side radius.
See figure 7
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Figure 6
Figure 7
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Second, for those who desire optimum exhaust flow, the "convertible" exhaust design allows
the exterior portion of the port to be removed back to the water jacket. This modification can be performed at the
time of sale, or later at a competent machine shop with an end mill. If desired, instructions can be obtained apon request.
Performing this process leaves a flange
which has bolt bosses cast for custom header mounting. With proper header design, this modification offers one of the shortest
exhaust port transition angles in the industry at about 60 degrees.
See figure 8
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Figure 8
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