do you have to run the cross over on the rear of the heads ......would like to plug them off would it run hot ?has anyone plug them???

 

It will over-heat... Its a steam/air cross-over tube....

 

Gotta have them to keep air out of the heads. Part of the LT1 cooling system.

 

There are holes that are pluged on the front of the heads (At least on my AFR's) if you wanted to move the steam vent to the front but you absolutly need it or you will overheat. BTW why do you want to block it off?