All these tests were done on Superflow test benches
at 25" depression, data corrected for atmospheric conditions. I've
highlighted the 0.400" lift line as this is what my Kent cam with 1.5
roller rockers achieves. Beyond that lift it's pretty academic, eh?
The first plot is for intake ports. As you can see,
the 8-ports are in a class by themselves, and the 5-ports are difficult to
distinguish, within the margin of error for the test method, until
0.030" lift when the Pierce head wheezes out. This could be corrected
with a bit of port work, but it works well enough out of the box. I should
note that the same Elder head casting was tested in Australia by Graham
Russell and by me here. Although the data should match up, Graham showed
higher flow at high lift and lower flow at low lift - a difference of 10%
crossing 0% at 0.025" lift. Maybe it's the Oz air? No matter, both
tests show the head has the potential to make serious power.
It may be a bit unfair to directly compare flows for
5 and 8-port heads. Obviously the port size for the siamese pair will be
much larger than the single runner on the 8-port. But, the Elder design is
comparable to the old Westlake design and it compares very nicely.
Unfortunately I didn't keep an inlet port cast from the Westlake heads
when I sold them so I can't compare port sizes. The Westlake has ports
coming down from the top of the head at 30° and really doesn't have a
short radius at all. The Elder comes in high on the front face and drops
to the valve at 17° so the short radius is less important than a siamese
head with a 90° turn.
My thinking at the moment is that the 8-port head
needs a completely different cam profile to the siamese port head. Since
the Elder flows really well at low lift, maybe a profile that doesn't lift
so high, but has wider flanks and more duration would maximize the area
under the lift-flow curve. I'll consult with Graham Russell about this and see
what he says.