can someone please explane tihs

It's all about getting as much air / fuel into the combustion chamber as possible. Lift refers to how far the valve opens. The cam lifts up the lifter and the rest of the valve train. The more it lifts, the more the valve opens into the combustion chamber. When this happens there is less restriction to the incoming air and fuel and therefore more can get in which produces more power.

Duration refers to how long the valve is opened up for. The longer it can stay open, the more air and fuel can get in.

The same in reverse order also applies to the exaust side. The more the valve is lifted the less restriction it has to the escaping gases, and the longer it stays open (Duration) the more exaust can escape, and when that happens you have room for the incoming air and fuel.

Ed

new84 said:

and also with rockers when thay say it has a 1.6 ratio what is the ratio of?and how dose it affect power?

Click to expand...

The 1.6 ratio refers to the cam lobe lift vs. the valve lift.

Basically, if the cam lobe lifts the pushrod 1" (thus moving that end of the rocker 1") then the other end of the rocker (the part pushing the valve) will move 1.6".

Of course, valve lifts are not that large. If a cam is advertised as having a .410" lift, the valve will open to .410" with a certain rocker arm...usually a 1.5 ratio. If you installed this same cam and used 1.6 rockers, the valve lift would increase to .437". The increased lift helps things as RTX explained above.