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In
supercharged, turbocharged or nitrous applications, this also means more
forced induction can be used with less chance of detonation. Also even though there is more exhaust valve area with the
two exhaust valves, it is accomplished with a smaller valve.
These smaller valves are less likely to glow red and pre-ignite the mixture
in severe duty applications.
Notice
stock head gaskets can be used, and all water holes are located in the exact
same location to come through the gasket as in a stock head.
Combustion chamber volume is 64cc standard. Can be varied from 58cc to 78cc.
Stock flat top pistons can be used from 9.0:1 to 10.5:1. For higher
compression ratios pop up pistons are available. Valve notches required if camshaft larger than
.550” lift and 244degrees
@050.
The
“B” heads for 4.0” to 4.060” bore size has valve sizes of: Intakes 2@ 1.650”
each. This has a curtain flow area (perimeter of valve X height of lift, the
actual flow window, of a single intake valve of 3.300” diameter. And Exhaust sizes 2@1.400”
each. This has a curtain flow area of a single 2.800” exhaust valve. This is
why the 32 valve heads can produce well over 100 hp more than the best
2valve heads on the market today.
The way this curtain
flow area works in the 4 valve per cylinder application is this. The
performance gain with the 4 valves per cylinder is not so much at peak valve
lift, (an engine is only at peak valve lift for a very few crankshaft
degrees), but the flow advantage it has all the way up to full lift and all
the way down after full lift. This is when the cylinder is getting more
fully charged on the intake stroke and more fully excavated when on the
exhaust stroke. For example, at only .050” valve lift the 4 valve head is
already flowing 50% more air than the 2 valve head at the same lift.
Also camshafts can be run that have a wider lobe separation and less
duration for the same application. The wider lobe separation purges less
intake charge straight out the exhaust when at low speed. This less purging
makes for more low end torque, less emissions, and less fuel consumption.
Also camshafts with approximately 10 degrees less duration for the same
application can be used. This still makes much more overall power than the 2
valve heads, but has the same RPM characteristics where the peaks occur.
Most of the time we prefer mechanical roller camshafts. This enables us to
run the spring pressures that enable the extra RPM capability of the 4 valve
heads. With hydraulics, the springs have to be lightened up to enable the
hydraulics to work properly and this cuts into the extra RPM capability. |
