<VV> Cylinder balance test interpretation

[Doug Mackintosh]

On the Corvair I am working on, I believe I have a collapsed hydraulic lifter on # 4 Exhaust. I believe the valve is being lifted some, since it is not blowing back through the intake as it does if I completely disable that valve. 
 
Today I tried a cylinder balance test (at idle) by shorting each cylinder out and observing the RPM drop. I was expecting to either see approximately equal RPM drop for all cylinders, or no RPM drop on cylinder 4. Instead, I found that 5 of the cylinders had similar RPM drops (approximately 80 RPM) but # 4 cylinder dropped around 240 RPM.
 
Why did it do that?

-- Doug Mackintosh
Corsa member since 1996
Corsa/NC member since 1996, Virtual Vairs member
Corvair owner 1969-1971 and 1996-on