I have been thinking about what I have to use. I do not want to bother my neighbor with TIG or stick, he has enough work to do! The MIG wire has an 45% iron core and 55% nickel cover. I have a BBQ grill, propane torch (small and large) and a bucket of sand.
After reading some sheets, recommended pre-heat is 350 deg (might need new gloves!). and end drill the cracks.
I have to weld a hole in a heat riser, so I will try the propane to get it up over 100 deg (some videos found about that temp), weld it, then in the sand. My shielding gas is mild steel mix argon75/CO2-25. Sheets say argon95/HE5 or argon75/HE25, but Helium is used to raise the temp, something we do not want here, so I will try the CO2 and see if I get good penetration.
For the real repair, I will have to wait for the ambient air temp to improve more (its still cold in the garage), before trying larger repairs.
It is just annoying to wait for spring, I wanted to finish up this smog restore months ago!
Its been one set back after another. Smog pump was tricky to de-vane, two smog tubes rusted on, bolts rusted on, now this crack. At least the pump is done, and got the smog tubes nuts out.
Now I need to repair two nuts on one smog tube, still get the lower bolts out, fab manifold plugs and after crack fix, evapo-rust the manifolds and coat.