When is an SFI rated balancer needed? How much hp/rpms can a stock balancer hold up to? I ask because the difference between the two balancers is around $190..
you only need the SFI rated balancer IF you are going racing, AND if you are going to turn 6500+ rpm on a regular basis. for the street you dont need it.
The car is going to be drag raced and street driven. Basically the goal is a street legal drag car. Will I be touring the US attending events? No. Probably just local tracks for test tune or classic drags. Peak RPM range is 5500-5800 rpms. The motor is a built 331. Hopefully I can get it into the low 12's, so is there a trap time that mandates it?
under 12's and 5500-5800 rpms probably will not require an SFI balancer but it's best to check the rules of the sanctioning body for the class you'll be competing in.
here are the NHRA rules concerning the use of an SFI balancer. it's still best to check the specific requirements for your class but they should all follow the same general rules.