It actually is a pretty serious exploit, not that you've done anything wrong if you haven't gone ig like that, just clarifying. The engine as you pointed out doesn't have a carry capacity defined for that value str, so it's like 0. However, if you were to continue doing what you've done, it doesn't have to be much lower for it to kick and give you an unbelievable carry capacity. I think somewhere around the 240 mark. Engine of destruction is one way of putting it.. lol
This of course would be easily noticed by a DM and anyone caught ig like that would face some pretty serious consequences, understandably so.