What power can standard internals take on a 2 litre classic impreza turbo 2000? Want to try and get near the 400bhp mark and I'm aware I will need z new gearbox (I'm on the limit as it is lol) but will my internals be ok or will I need to change anything else? Thanks in advance.

 

Sorry to say but 400 will kill the bottom end,you need a forged motor ie pistons/rods and uprated bearings to make it last anytime.

 

or a newage sti motor

 

 

I wouldn't want to run a standard UK engine at much over 300 let alone 400.

 

even at 300bhp..+ you are playing a dice game.

 

It can depend on how the engines been maintained and how its used imho.I have been running 330 bhp for 2 yrs now on std uk internals and car still hit 6,791 rpm with Bob rawle last weds ,when having the map tweaked.,and the car has run faultless since i have owned it.
Why would anyone want to try and achieve 400 bhp on a std uk car as it is almost certainly going to end in tears..Much better to start with a stronger engine in the 1st place and work from there imho.,and as stated above.
I only know of 1 classic uk car that is running 415 bhp , on bog std uk internals and it has done this for the best part of 7yrs with a 6 speed gearbox and is still running to this day iirc,so you can get exceptions to the norm,but would you personally want to risk it.