White smoke
 

Just changed the valve cover gaskets because I want to clean out all the old gunk that was in the covers, so glad I did it was horrible. So now my 92 Blazer 4.3 TBI is blow a lot of white smoke out of the exhaust. The week prior I changed the thermostat and temp gauge and the truck finally got up to temp for the first time since I owned it. The day I changed the valve cover gaskets I noticed the top Radiator hose was sucked flat and the coolant level was low, so filled it up, only maybe a quart of 50/50 coolant mix and now its blowing white smoke. I'm hoping not a cracked block anything else I can deal with. What might it be?