Originally Posted by KAT-PWR

I'm going to say around 400hp is where things really start getting sketchy. Nissan cast pistons ka/sr have always been the weak points. I'm going to guess SR/KA pistons and rods are made via the same processes. The pistons tend to give out well before the rods do. Weak ringlands break especially with mediocre tuning.
I would upgrade pistons before I upgraded the rods.
I know ka rods are larger than sr's rods but I'd bet the power handling capabilities are similar.
Rs-enthalpy has advised me to not take stock rods over 450WTQ and at that point you'd be really stressing the pistons. Which is why I say upgrade pistons before rods.
For example in my current set up I made 400whp but only 340WTQ, forged pistons on the stock rods. I am about 100wtq shy of the advised 450wtq cut off. I'd probably be making in the mid 500's by the time i hit 450wtq, which is not going to happen with stock pistons.*
*Yes there are examples of people making more numbers on stock motors but those are the few. I am speaking generally.