I have had to do the head gaskets on my Ford Van (351W V-8)
During the process of tearing down the manifold the thermostat case bolt sheared in place.
The manifold is aluminum and the bolt mild steel.
It took several try's to get the remaining portion of the bolt extracted from the manifold but eventually I won .
I will still have to chase the threads with a tap and purchase a new set of bolts but for now the job is done.
I have a foot pedal for amperage control so although the machine was set around 140 amps I would bet I barley used 60 for this project.
I allowed the heat to "soak" into the bolt for several seconds before adding filler metal in the hopes of getting more shrinkage with the addition of filler metal as well as to insure adequate fusion. I used ER 70S-2 filler in 1/16" diameter for the build up.
The torch was set up with a 2% lanthanated 1/8" Tungsten with an extra long tip (roughly 3X the width in length) to focus the arc where I wanted and not on the aluminum intake. I could have used a smaller electrode but I was to lazy to change the collet body out. A 3/32 Tungsten similarly sharpened would have been better for a lesser experienced welder as it would provide a larger margin for errors in amperage control.
When doing this type of project the most important detail is in letting the heat "soak" for a few seconds until an adequate puddle has formed on the bolt before adding filler than, add a little and taper off the amperage a little to allow it to "freeze" before ramping back up and adding more , pause and repeat as many time as necessary until you have enough built up to get your vise grips or whatever on the welded stud.
Another technique is to build it up a little than weld a nut onto the welded stud so you can get a wrench on it. I find either effective and take about the same amount of time and effort.
HAPPY WELDING .
