My question is this. **What are the similarities and differences between the M3's S14 engine and the 318is M42 engine(apart from displacment)?** They look very much alike from under the vavle cover!! I was thinking that with the high cost assosiated with the E30 M3 S14 engine could one simply swap the S14 for a M42. With the cost difference, one could easily develop a nice intercooled turbo setup giving the M42 in the same power (or more) than the S14. This would retain the weight ballance of the 4 cylinder E30 M3. One could drive the hell out of it and if it breaks, simply find another M42 engine.