Say you have two cams that have an RPM range of 2500-6500 rpm. The one has a duration 300/300 Advertised and a lift of 515/515 and the other 295/295 and a lift of 534/534. Everything else being the same, which one would make more power? Is it in the duration or lift? I know there's other variables like LSA, but all that stuff being the same.

 

Sorry, i wanted to put this in tech/general engine.

 

Assumption #1: The heads will flow more at .534 than they will at .515.

Problem with Assumption #1: That's rarely true, especially on factory heads.

Assumption #2: The other characteristics of the cams are identical.

Problem with Assumption #2: That's rarely true.

 

It depends alot on the shape of the lobes. There's alot more to a cam than peak lift, which is the only number usually given. The "area under the curve" ultimately determines how much power the cam will make. The duration and lobe separation as well as where it's installed (intake centerline) will determine what RPM it make that power at.

A cam with lots of duration and lower lift usually has slower ramps which means that at all times the valve is open less. Less opening = less flow = less cylinder fill = less power. On the other hand, faster opening = more stress on the valve train = shorter life. Ever watch a NASCAR race? Well let me tell you something.... those guys know how many times that engine is going to turn during the course of the race. It's going to go 4100 revolutions per mile, or 4600, or 3700, or whatever, depending on the track.... they pick the cam that will make the greatest possible power, but still make it to the end of the race, and be completely wiped out at the end. I doubt most of us (a few maybe, but not most) would pick a cam for their street car that way. You don't see as many 495 mile motors trying to run 500 mile races as you used to, but it still happens.

What does it mean when a cam "has a power range of...."? Does that mean that it produces any power at all; or that the torque is within 10% of the peak; or within 50% of the peak; or what? Kind of reminds me of those intakes that claim a power band of 0-7000 RPM. Not in this unverse, bro.

Cams are one of the most complicated things about how to tune an engine combination. The specs you have given aren't enough information to answer the question.