How much power do you think is safe on stock internals?

BGTV8

You are actually asking the wrong question, as the proper answer is "it depends" - mostly on the duration that Wide Open Throttle is held given a specific power setting. It can also depend upon the load generated in the mid rev-range when you go from steady state throttle setting (usually around 15-20% throttle position) to WoT, especially when revs are high enough for a FI setup to be capable of generating peak boost.

If the ignition map is not top-notch, all it will take to kill the engine is one or two "knocks" (detonation's) - you break a piston, or bend a rod which cause rod-breakage and catastrophic engine failure.

My mates at Air Power Systems reckoned on the Z33 that their TT kit was safe (their word was "durable") for ~300kw atw with stock internals. This is ~400hp atw. Since the Z34 shares a similar bottom end, I reckon this is not far away.

I am not saying that you cannot tune for higher numbers and not kill an engine, because if the car is a dyno-queen and only ever pulls numbers on the rollers, then the full load only exists for a short (small number of seconds) of time, and you can set knock control to be very conservative.

With a more aggressive ignition map, engine life at similar power levels might be milliseconds.

IMHO - the question is not valid as it needs to be more fully qualifed, as most of the later posts have indicated ... it is about "how long" you expect the engine to live.

RB