also i may be wrong but turning the crank to TDC also stops the valves falling into the cylinder
yeh i'd thought about that but you'd need to do 2 cylinders ie 1&4 with engine at tdc, then with the chain loose on the crank and obv not on cams rotate engine so cylinders 2&3 are at tdc, sketchhyyyyyyy.
unless you swapped 1&4 springs, cams back in, rotate engine, springs 2&3 cylinders....balllache!!
however peak bhp doesn’t directly relate to real world driving enjoyment day to day.