How hard is it rebuild 1999 i6 motor?

 

depends on what you wana do with it if you wana do over sized pistons then it will be hard you might have to take it to a machine shop but if you just wana put new rings and reg pistons in and all that its easy just time consuming make sure you have everything to spec or you will be screwed

edit: remember to get all new bearings and stuff do a full rebuild with all new stuff like valves and cam/crank shafts and im not positive but if its a push rod engine get new rods good luck dude