I recently purchased a Fp green for my 03 VIII and i was just wondering how high you can go (hp wise) before you have to start building up the engine?
i'm putting on the green with a ebay o2 and porting both and the exhaust manifold.
i figure i'll be somewhere in the range of 410-425whp since i made 349whp with the mods in sig.
So when do you need to starting building up the engine?

 

depends on tune and milage of the vehicle. also what you do. i made about those numbers with my green and my motor held up good. it also had 70k on it and the last owner beat the car and overheated it twice. i also raced it at the drag strip 3 weekends a month.

 

It's unlikely that you'll be in the 400s on a green unless you got the HTA or are running meth or e85. Anyway, you should be good on the build, many people running around with 500 hp on stock internals and head.

 

your engine will hold more then the Green if tuned right.

 

as stated above the motor is probably good for more than 400whp. the tune is the key