Because you have 2 cylinders sharing just one intake port, and they have a tendency to rob fuel from the shared cylinder because of this design. You'll have one of those cylinders set to start drawing fuel into the cylinder and then the siamese cylinder will start to open its valve and draw fuel in from the other one, robbing it of its full amount of fuel meant for the first one.
I just went out and thought it through. I don't see any reason it shouldn't work. The neighboring cylinders are on opposite parts of the stroke. Like while 1 is on the intake stroke, 2 is on the compression stroke.
69 Buick Special Deluxe. Intercooled Turbo Chevy 250 @ 15psi on a stock long block. It's kinda fast.
