For the most i think 700bhp on a healthy stock engine will be fine if you look after it and dont do to many top speed runs, it is a risk but as long as you are aware of it thats fine, both times i have had problems with my stock and built engine was at thunder road, i pushed that stock engine hard and it never liked it in the end, i knew my built engine had a problem before i even raced at thunder road but as i was taking it apart the week later for the winter upgrades i took the risk and ran it, we think the block had a crack as every time i went flat out the water system pressurised and overflowed, i got that block out of a crashed supra. running a 50shot of Nitrous off the line and in every gear on top of 900bhp might have helped finish it off, i cared not as i wanted to upgrade the engine anyhow.