How to model an engine v6 in SOLIDWORKS?
3 Answer

first you should made its bottom casing , then the crank and after piston assemblies . . or you can do is fist make crankshaft and the whole model will be respect to that part .
Answered with a tutorial: https://grabcad.com/tutorials/how-to-model-an-engine-v6-in-solidworks

tutorial video V8 https://www.youtube.com/watch?v=CViLe1NG63k&index=59&list=UUEcQmIBzGyMD_IdH14QTWbQ
Maybe can help you