This may be a dumb question but how is duration calculated? I searched on this and did not find an answer to my question.

Just gonna make up some numbers for example.

Cam with 1.5 rocker is 230/230 duration and .500/.500 lift.
Cam with 1.6 rocker is ???/??? duration and .533/.533 lift.

I am assuming because the lift is changing that the duration is as well,true?

 

Rocker only changes the lift, I believe the duration is determined by the cam lobe design.

 

It will have a minscule impact on duration, not enough to bother discussing.

 

Why? Wouldn't the lifter still land on the base circle at the same time?

 

rockers wouldn't change duration at all, only lift and ramp rate. since the rocker has to open the valve further in the same amount of time (duration) it actually opens the valve faster. no impact on duration. no impact on duration. i sound like my dad.

 

So you guys are arguing that a higher ratio rocker won't cause the valve to hit .050 lifts sooner or delay the point when it comes back down to that point??

The difference is miniscule not worth arguing but it does impact duration at the valve.

 

Ok, so either way not worth discussing. Thanks for answering my question

 

I'll give you that one. If you measure at .050, it would make a tiny difference. If you measure at zero lash though (which is what the valve actually does), it would be the same.