In theory, yes. It only takes money. If your 318i is the single cam motor. Then you need a motor transplant. i.e. the M42, which was the road going block. You could then bolt most of the performance bits straight onto that block. The 'S' on all BMW block denotes it is the performance version. For example, an E30 M3 has an S14 block. There are 200 road going 318iS with the S42 block somewhere.