just out of interest what can the standard lump from a uk 2.5ltr sti / RB320 take? its safe limit not a forged build. for example the late classic sti lump can run 400bhp (but for how long) where the 350/350 mark seems to be within its safe limit that most tuners would agree to. what is it for the newage 2.5ltr lumps? i am sure some of you are runnig 450bhp+ on them but is that not pushing it too far? where as for example 400/420 would be classed as the top end to go on std internals without the chance of a rod or beraing letting go (if any of that makes sense)

regards

 

you can run a good 350bhp with 400 ft/lb torque

 

Aren't the heads a limiting factor to big bhp on the 2.5?

 

Not that I have seen

550bhp & 600 lb/ft on my std UK 2.5 heads with the MD321V turbo.

Std engine will cope with 400/400 (and a bit) without too much problem if mapped det free.

 

The piston design is the biggest weak spot (along with the head gasket and even dodgy cylinder liners) were the biggest issues, the materials used on the pistons is not an issue (as seen on the jdm cars as their piston design is different being 2ltr) so this limits your power unless you upgrade the internals (also the cranks are not similar to the jdm cars which are uprated for better oil distribution).
350 is safe, 380 is about as far as you want to go, 400 is very border line, later (new shape cars) supposedly have a different piston design so are stronger

Tony