found a 160 amp alternator in my parts building and I'm thinking of using it as an on board welder. What do i need to do

Check out this link:

http://www.pirate4x4.com/tech/on-boardwelder/index.html

I'm thinking of doing the same thing. I think you can do something inside a GM alt. and just hook up some heavy gauge wire to the alt for welding cables. I'll see if I can dig up some other links...

This fella did a great write-up using a delco alt.

http://www.geocities.com/Yosemite/2472/obweld.html

Think READY WELDER all the way!

Danny bought one of these about a year ago, and our wheelin' group has already gone thru a 3lb spool of wire fixing trucks, ATV's, Trailers! We've done trail repairs on everything from oil pans, tie-rods, shock mounts, drive shafts! Just ask Azrockcrawler (Chris are you still running that shaft?). For the size you just can't beat it!

Be careful about the Alternator versions. Unless you wire them very carefully (isolate the box) you CANNOT weld on your own vehicle (remember you run most stick rods NEGATIVE polarity)! Danny thought he had his Premier wired correctly, and burned out the control box. Then, not only was he unable to weld on his truck, the alternator stopped charging the batteries. He ran his batteries down on the trail and never knew the box had been cooked until it was too late! :(

I can borrow Danny's about any time I want to. But, whenever I scrape a few extra dollars together I'm gonna get a readywelder for myself. I can run it off my TIG powersupply as a spool gun at the house as well...

here is another good write up:

http://www.huv.com/jon/jeep/Welder/alternator.html

thanks guys for all the info