Camshafts The Basics. What Does All Those Numbers And Terminology Means?

There are four main things to look at when buying a performance Honda Acura camshafts, duration, lift, overlap and lobe separation angle.

Duration is the number of degrees of crankshaft rotation that the valve is held open by the cam. The cam spins at half the engine speed and the total four stroke cycle is 720 degrees or two complete rotations of the crankshaft. The more duration camshaft has the more top end power is produced by the engine for the expense of the bottom end power. With lower bottom end power the idle becomes higher and rougher. The more duration cam has the longer the valve stays open and the cylinder has more time to be filed. This is important at high rpm because the higher the rpm, less and less time the cylinder has to get filed with air and fuel.

Lift is the height that the valve is lifted of the valve seat. The bigger the lift of the valve the better the flow is. The only problem with more lift is that valve float becomes a risk. Valve float is when the opening and closing speed of the valves becomes so fast that the valve spring can not keep up with the valves motion and they float away from the cam profile. If valve float is present there is a risk of piston hitting a valve. To prevent valve float stiffer valve springs must be used. Light weight titanium valve spring retainers are needed to reduce the internal forces that contribute to valve float. More lift will increase the top end power but will decrease significantly the bottom end power output.

Overlap is the period of time when both the intake and exhaust valves are open at the same time. Overlap helps the exhaust gas leave the engine easier. Too much overlap will make the intake charge rush out through the exhaust port, wasting fuel and making the low end power decrease. Most of the stock Honda Acura cams have a very little overlap because of strict pollution requirements.

Lobe separation angle is the number of degrees that the points of highest lift on the intake and exhaust cam are separated by. This is a useful number when dialing in your cam timing, which is an operation that should be done when building a performance Honda Acura. The lobe separation angle is directly connected to the amount of overlap an engine has. A smaller lobe separation angle has more overlap and a bigger angle has less.

So if you understand all the numbers, you know that a high lift long duration set of cams have a good power output at high engine speed but a poor idle and bad emission at low rpm. For most performance Honda Acura enthusiast a good choice for street driving is some where in the middle, compromising between the smooth idle, clean burning and good low end torque of a stock cam and the performance high rpm of a race cam.

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