long time reader finally need some help. just wondering what if anything would happen if i block off the input and output for the heater core at the block. thanks in advance got to get this running by the end of the day.

 

I would pull the hoses off of the firewall and connect them with a piece of pipe so as the flow just loops around. Not sure what would happen if you just blocked them off.

 

Yes better to loop the two hoses for the best flow for cooling