Event Coverage exhaust manifold

I have a exhaust manifold off of a 292 and it has a hair line crack. The crack is in the center down low not on a bolt hole. Ive been told you can weld it, you cant weld it ,JB weld blah blah blah..... whats the right way to fix it or can it even be fixed...thanks

 

It can be welded with "ni rod" and an arc welder, but it will crack as it cools if you don't do the job with a pre-heat and an after- heat.
Build a fire with charcoal in a vented container large enough to hold the manifold.
After veeing out the crack and stop drilling both ends of the crack, place it on the fire, making sure you have enough charcoal to get it good and hot.
Weld up the crack after you get the manifold HOT and have removed from fire to weld.
While welding crack have an assistant to add more charcoal to the fire. When welding is completed, place manifold back in the fire and cover with more charcoal.
Then cover the fire with a cover and allow just enough venting, in and out to maintain the burn at a slow rate till all the charcoal is consumed and the manifold cools SLOWLY.
When all this is done and the manifold has finally cooled down, the allover heat should prevent cracking from stresses in the casting, but you may find it is warped enough to require a trip to the milling machine for a true-up.
Dave