1. Field of the Invention
This application concerns a method for designing a family of DOHC (dual overhead camshaft) type cylinder heads for an internal combustion engine, each with different included angles between the intake and exhaust valves but utilizing a common casting, common valves, and common camshafts. More particularly, the family of cylinder heads has a camshaft drive apparatus including a pair of gears, one on the end of each camshaft, and a third driven gear which meshes with the other gears. Within the family of cylinder heads, the included valve angle is varied by the relatively simple process of changing the spacing between the camshafts and accommodating the resultant change in spacing between the camshaft mounted gears by shifting the axis of the driven shaft with respect to a plane extending through the two camshafts.
2. Description of the Related Art
Engine cylinder heads having dual overhead camshafts commonly rotate the camshafts by belts, chains, or gears. Often a combination of belts, chains, or gears is used. It is known to mount a gear on the end on each of the camshafts and to use another gear to drive the camshaft mounted gears. In a typical development phase for an engine, several cylinder heads are created and tested. These cylinder heads have different included angles between the intake and the exhaust valves. Previously, this was accomplished by moving camshafts laterally and/or vertically and accommodating these changes by providing different sized valves, different sized gear sets, and sometimes different camshafts. This process is very costly and time consuming as these components must be custom designed and ordered.