Camshaft Comparison - Cam Tech

Keep in mind that this particular test moved both the intake and exhaust lobes when increasing the lobe separation angle from 106 to 114 degrees. This also changed the opening and closing points for both the intake and exhaust. Since the intake closing is the most important, note that the 114-degree LSA also creates the latest intake closing point. This tends to improve top-end power. If we add the exhaust closing and intake opening point numbers at 0.050-inch tappet lift, this will deliver actual overlap at that checking height as shown in the chart. An interesting test would have been to retard and then advance the 110-degree LSA cam by four degrees. Retarding the cam would maintain the overlap yet put the intake closing point at the 45-degree ABDC that would duplicate the 114-degree test. Advancing the cam would have placed the intake closing at the 106-degree cam position. Those results would have allowed us to see the difference between overlap and the effect of intake closing. Basically, the wider (114-degree) lobe separation angle lost torque in the midrange compared to the tighter 106-degree LSA but made up ground with top-end power. Our contention is that the 114-degree LSA's better top-end power came as a result of the later-closing intake valve and not because of the reduced overlap. This tends to support the idea that a tighter LSA with a later-closing intake would be the best of both worlds. The price you pay for this would be greatly reduced bottom-end torque and a more erratic idle.

As you can see, there are a number of variables present in each and every camshaft that can be used to dial in the ultimate power in a street or race engine. Each engine will respond a little differently to these changes, but this test illustrates how overlap does have a positive affect on power.