Crossflow heads are more efficent for breathing (ie.horsepower), most foreign inlines are that way. No compromising the configuration, lengths,or routing of the individual port runners (be it intake or exhaust) since they are on opposite sides of the engine. However, the non-crossflow design lends itself to more utilitarian usage with its more compact design (carb heat for example is easily accomplished with a non- crossflow). A little more thought (and plumbing) must go into turbocharging a crossflow inline compared a non-crossflow. The turbo non-crossflow can be a very neat package (especially a draw-thru) since the inlet and outlet are conveniently nearby. Checkout virtually every vee type engine-all crossflow (easy for them-almost a necessity).
Crossflows are not a necessity-they just make it easier to make hp. Is it me or what, but it seems odd that both the Kirby-Sissell head, and the Duggan head are not crossflows. Thats a large undertaking with a lot of design time not to incorporate crossflow into their finished product which is supposed to a horsepower maker-it makes the designs of Wayne, Horning and maybe Herbert a bit more serious. As they say "my two cents thrown".
