When ordering a cam, do you folks recommend getting one with a little more duration and advancing it a few degrees, or less duration and installed straight up? Assuming the same heads, lift, etc. they should have similar power bands, right?

 

Nope, they will not have similar powerbands.

A larger duration cam will like a little bit more advance. There is a very popular LS1 cam out there that's big in the duration department, but has some advance ground into it to make up for it.

A larger duration cam will like the advance because it will raise the DCR due to the fact that it's moving the ICL and intake valve closing point.

My cams for LT1's are different from the popular C306 and other "large" cams and it all has to do where you put the cam in the motor and overlap.

If you have the same cam, advancing will lower the RPM band, and retarding will raise the RPM band. The stock LS6 cam is a 204/218 on a 117.5 retarded 2.5 degs. The high LSA and retard help make the intake valve closing point pretty late for a 204 duration cam so that's why it makes good power. The OMC from Thunder works under this same principal. Less duration and retard the cam to get the intake valve closing point in the right spot for High RPM power.

Bret