Not much to see or photograph yet. What we've done is to slice up a couple of heads on the bandsaw to see where the ports really lie and how much iron is in there.
The casting on a D3 head is surprisingly thin, but I think that's typical of all of them. Still, there is enough there to do some improvements on the intake. Probably the biggest gains will come on the exhaust side.
The interesting thing about the small six head is the high port configuration on the intake side. If you slice the intake straight off, the ports are straight, direct, and have no impediments to flow. There is some casting flash and some pocket work that helps, but this port could probably flow very, very well with good valves and a little porting.
The exhausts, however, are lousy in stock form. There is a dogleg turn leading to the flange in 1, 2, 4, and 6. 3 and 4 are siamesed to provide a heat riser. All of them lack enough cross sectional area to provide any flow, and the area under the valve is so restricted that it would be barely adequate for a lawn mower engine. I think that's why these engines respond so well to port dividers and headers. It's a poor performance design, but we think there's a way to make it really flow.
Joe and I have some ideas on how to make it work, but frankly, I have no need to build an engine like this and too many irons in the fire right now. Maybe after we get the Crossflow running we'll tinker with it some more.
