Here are a few head design samples for comparison.
Take note of the Chrysler's hemispherical combustion
chamber, which creates better thermal and volumetric
efficiency. The valves are located across from each
other, not side-by-side, to allow better air flow of
the intake and exhaust gases. Also note where the
spark plugs are positioned, where they can provide
maximum ignition combustion in the chamber.
Chrysler 426 Hemi Cylinder Head
BMW 2002 E12 Cylinder Head
Chevrolet 427 Cylinder Head
Ford 289 Cylinder Head