This is the kind of damage...
This is the kind of damage that can occur when your engine goes through detonation, or pre-ignition. The forces generated can wreak havoc to the valvetrain and cause this type of premature wear on the cam as the lifters are slammed into the camshaft.
BTDC - Before Top Dead Center, the piston is traveling up in the bore toward TDC, measured in degrees of crankshaft rotation.
Cam Lifter or Tappet - The mechanical interface between the camshaft and the pushrod. The lifter or tappet can range from having a flat surface or a roller riding against the cam to transfer cam action into the valvetrain.
Cam Lift - This is the amount of distance the cam pushes the lifter above the base circle diameter. This is not to be confused with gross valve lift, the distance the valve will be lifted off the valve seat.
Coil Bind - A condition where the valve spring has been compressed to the point where there is no longer any clearance between the coils. At this point the spring is no longer a spring but is effectively a spacer.
Degreeing the Cam - The act of checking the synchronization of the camshaft's position to the crankshaft position, accomplished during the assembly process.
Dual Pattern - A camshaft having different cam profiles on the intake and exhaust lobes.
Duration - The length of time measured in crankshaft degrees that the valve is held open by the cam.
Gross Valve Lift - The amount of distance the valve travels from the closed to the full open position, measured at the valve.
Hydraulic Lifters - Lifters designed to maintain zero clearance in the valvetrain mechanism. This is accomplished by using engine oil pressure to actuate a set of pistons and seal cups in the lifter.
Lobe - This applies to the cam's shape. The lobe is the eccentric portion of the cam and transmits the lifting motion through the valvetrain to operate the valves. The design of the lobe determines the intent of the camshaft.
These cam bearings were installed...
These cam bearings were installed at the factory in an LS engine. They have a visible seam, and many engine builders prefer the seamless bearing over this type. For the purpose of a racing engine, the seamless bearing is the way to go.
Lobe Area - Used for comparison of various lobe profiles. The figure is obtained by adding the lift at every degree of rotation. This will give you a numerical picture of the lobe, or if you plot the lift versus position in a spread sheet you can get a graphical representation.
Lobe Center - The distance measured in degrees between the centerline of the intake lobe and the centerline of the exhaust lobe used to operate the valves in the same cylinder.
Net Valve Lift - The actual lift of the valve. It is the gross valve lift (lobe lift multiplied by the rocker ratio) minus the amount of lash you have at the valve.
Nose of the Lobe - Highest portion of the cam lobe away from the base circle of the cam.
Overlap - Situation where both the intake and exhaust valves are open as the piston is traveling towards and away from TDC on the exhaust stroke. Overlap is measured in crankshaft degrees.
Ramp Rate - The speed that the valve opens and closes.
Roller Lifter - The roller lifter performs the same function as the mechanical or hydraulic tappet. However, instead of sliding on the cam face, the lifter contains a roller bearing which rolls over the cam surface.
Valve Float - When the rpm is too great for the valve springs to control the valve action. At the point of valve float the valves will "float" out of sync with the action of the cam. The valves will loft over the nose of the cam.
Valve Lash or Clearance - The clearance between the base circle of the camshaft lobe and the lifter. The lash is measured at the valve.