judgez24

Ok guys lets break it down real easy.

Lift Duration

Duration refers to how long a valve is opened in relation to crankshaft rotation/s. This open valve time period is expressed in degrees of crankshaft rotations. So, a cam specification of 244 degrees duration simply means the cam holds the valve open for 244 degrees of crankshaft rotation. As a rule, more duration can be helpful in high rev engines but not low rev engines. The extra degrees of open valve time in high rev engines gives the air flow a little more time to get into (or out of) the cylinder in spite of the piston's stroke. However, at lower revs, more duration can cause less power because the valves will be open at the wrong time in relation to the piston's stroke up or down in the cylinder.


Lift (Lobe Height)

While Lift durations refers to how long the valve/s is opened, lift is used to find out how wide the valve is opened. If the valves are not opened wide enough, they will cause a restriction or bottleneck to say for the air trying to enter or exit the cylinder. BUT, opening the valve past a certain point will not increase the flow to (or from) the cylinder.

Centerline

The cam's centerline spec is used to tie the valve timing to the crankshaft's rotation. This spec is expressed as the number of degrees the crankshaft must rotate from top dead center until the cam has rotated to the peak (or centerline) of the lobe. The centerline spec and the duration spec can be used to calculate when the valves open and close in relation to the crankshaft's rotation. When the valves open (or close) relative to the crankshaft's rotation is known as valve events or valve timing. Understanding the effects of valve events or valve timing is the real secret to understanding engine performance/tuning. For the engine to run at its peak performance, the valves must open and close at the correct time in relation to the piston's position and the crankshaft's speed.

Separation

Separation refers to the spacing between the intake lobe and exhaust lobe on the cam shaft. The SOHC cam on the Isuzu, neon, or an old quad 4 engine is the only one that will have this from the list above. This spacing (or separation) is shown in degrees on the cam, not on the crankshaft. So, a 108 lobe separation means the intake and exhaust lobes are 108 degrees apart from each other on the cam shaft. This spec by itself really doesn't mean much. Separation, just like centerline, is another way to tie the duration to the crankshaft rotation and end up with valve events/movements. This spec is a little more complicated though, because it is in cam shaft degrees and the crankshaft rotates two degrees for each one degree of cam rotation. Also, if the cam has been installed either advanced or retarded, the valve events/movements will be different.

So all Of What I just explained should break down how a cam, or CAMS work on any application, whether it be a push rod, or CHC

n1gro

I always knew what a cam was, but not its exact purpose, not enough to break it down technically. Thanks for the lesson brother.

Adli

Good Post

judgez24

glad you guys liked it, now go talk smart car talk to your friends

kentm

Thanks for posting that, someone like me could always use more info. I like using howstuffworks.com as a good reference as well, I leraned how differentials and rotarys work on that site.