Cam degrees.. Explain??

[Anonymous]

Could someone please explain the differences in cams. I see cams for sale with, for expample, 290 degrees. I hope i dont sound 100% thick, but i dont really know what it all means.

What should i be looking for. The one mentioned above was a shrick cam. Are these any good?

Cheers Paul :-/

[Anonymous]

I think its the angle in one 360 degree rotation that the cam lobe keeps the valve open, i.e the valve is open for 270 degrees in one rotation.

Not entirely sure though but am interested to know aswell.

[Anonymous]

Cam characteristics are defined broadly by:
1. Duration (as Cornish says)
2. Lift (the actual max.distance that the valves are forced open to)

"Performance or hot" cams generally have a combination of greater duration and lift i.e the valves open further and stay open longer to facilitate greater airflow. The relationship between the 2 is quite complicated and the max. lift worth using for max. power is related to the bore size ( I think?) In many heads (such as the SOHC Vaux 8v)duration is more critical than lift. In the DOHC 16v, overlap ( easily adjustable between the 2 cams) is the area to concentrate on. As far as i know all engines have some degree of overlap( a duration when both the inlet and zorst valves are partially open together ). The idea is that at higher revs the escaping zorst gases actually "scour" out the cylinders improving the airflow into the engine and the performance. As you travel further along the tuning path the subtle interactions between the various components involved in carrying gases into and away from the car become increasingly important.