Can someone explain to me in a reasonably simple way how the torque figure is worked out on an engine build. I understand what it is and that it can be measured/calculated on the rolling road but do people actually work it out prior to the build of an engine based on parts they install etc.

I am building a zetec turbo (Silvertop) with Wossner piston etc and looking to run at around 320bhp. I have fitted an ST170 box and looking at clutch options but as the clutches are rated in torque figures i am not sure what a zetec turbo at that BHP will produce. If anyone has any figure they can share it might help me get an idea for what i need but i assume people don't just build these engines any guess the torque figures for the clutches or is it all just experience?

Stay safe.

Adam