The main initial change was to reduce the valve angle to 90 degrees for a more compact combustion chamber.

Around 1954, the "B type" head appeared, with equal valve angles of 35 degrees on inlet and exhaust.

The valve angle was changed for better breathing.

These engines, while being a wedge-head, had a unique combustion chamber that resulted from a valve angle of only 6 .

The valve angles are identical to the Ducati 1098.

The included valve angle was reduced from 40 degrees on the 996 to 25 degrees on the 998.

The included valve angle was progressively narrowed, and the crankshaft strengthened.

It had four valves per cylinder, 90-degree valve angle and twin-spark ignition.

In a departure from previous Ferrari designs, the valve angle was reduced three degrees to 54 for a more-compact head.

The valve angles would be so crazy that the head would be nearly impossible to design.