GOOD READ

**Lift**

Lift is the measurement of how far the specific camshaft will open the valves. You usually have a lot of room with this number, as long as you don't go too far where the valves come in contact with the pistons, but running a cam big enough to contact the pistons is not likely at all and not practical at all. These numbers usually are shown asssuming a 1.5 Ratio rocker arm, meaning that if the cam lifted the one side of the rocker arm .300 inches, the valve side will be pushed down .450 inches (.300 x 1.5 = .450). Thus, when you buy the cam, the first number listed will be .450. If you upgrade your rockers to a 1.6 Ratio, that same .450 camshaft will lift the valves .480 inches (.300 x 1.6 = .480). That is why you can simply change out your rockers if you do not want to invest in an entire cam package and your stock cam will perform as if it was a bigger cam. While lift does not exactly translate to power, it does help. However, judging a cams performance is not a measure of its lift as much as its duration.

**Duration**

Duration is simply how long during a full rotation of the crankshaft that the valves will stay open. This is what determines how an engine will perform when it comes to a camshaft. You can have the most lift in the world but if you do not have a correct amount of duration for you application, you will be greatly disappointed with camshaft performance. Too much duration, and throttle responce will go down across the board and you will be left with an engine that is slow in both low-end and high end power. Too little duration, like in the stock camshafts, and high end power is decreased. In general, it is best to run a low duration camshaft in a street car (somewhere around 220-230) because you will have increased idle vacuum, and therefore better throttle responce, especially since street driven cars rarely see high RPMs. However, if you are building a drag engine, you are going to want a higher duration camshaft because you will see a large increase in high end power and a transbrake/ stall will allow you to launch at these high RPMs.

**Lobe Separation Angle**(LSA)

The LSA of the car is the difference, in degrees, between the point of maximum lift on the intake lobe and the point of maximum lift on the exhaust lobe. This number can vary greatly, and it again depends on your goals for the car. Most cams come with an LSA anywhere in the range of 104-115. If you are simply looking for a cam based on the sound it produces, this is what you want to look at. A lower LSA, such as a 108, will produce a much choppier and aggressive grind then say a 114 LSA. However, there are many other factors that the LSA will effect when it comes to engine performance. A low LSA will result in more torque in the engine, but the torque curve will be wore peaky and not as flat/ stable as a higher LSA cam. This means that you will be making more torque at a certain RPM with the lower LSA, but it will fall off quickly. A higher LSA will produce a lower peak torque number, but you will be making good torque throughout the power curve, which is why even though a low LSA may sound good in a car, it is not ideal for a street driven car.

Shelf grind camshafts are not the only way to go, however. Many people decide to go with a custom ground camshaft so they are sure it meets their specific goals for the car, and with a little research and aplication of the information above, you can deisgn your own custom cam.

An example of this would be someone who wants to retain the stock throttle responce and streetability, but at the same time wants that agressive idle. They can have a custom camshaft ground that has similar numbers to the stock cam, such as a 20x duration and 45x lift, but drop down to a 112 or 111 LSA. The torque curve will be slightly modified due to the lower LSA, but because you are retaining your stock duration, your throttle responce and power will stay near the same.

The second example would be the adverage street car. Someone who is looking for power gains but at the same time a streetable RPM range. This type of driver will be looking for lift numbers between .52x and .56x, duration between 22x and 24x, and the LSA depends on their goal for the idle of the car, but most do not want to drop below a 109 or 108 LSA or else the idle will be too rough for a street car and driveability will be greatly reduced.

The third and final example of this would be a drag car. These are people who have a much higher RPM range and therefore, can run larger cams without worrying about the rough drive home. Lift numbers for a cam like this should range from .57x to .61x. Duration can be higher than normal, and most choose to run 25x all the way up to 28x. Extremely low LSAs are also attainable, and most run anywhere from a 104 LSA to a 108 LSA.

 

that was a great read.....sticky Material IMO if its not already..Thanks

 

Stock L33 5.3 with that cam and headers. Thanks for clearing things up!