by 55panman » Thu Jun 07, 2018 10:08 am
Erik, Regarding your advise on welding alum. heads. You say you have to relieve deep into the crack. You HAVE to make sure the crack is completely gone. If you DON'T it WILL return later. Much of the time that means going 100% through to the other side. The crack may not look like it comes through to the other side but as you put heat to the metal the crack may propagate through to the other side and will, as I say return after you've put the part in service. I was a Boilermaker, Nuke certified high pressure steam welder by trade. One tool we used quite often is NDT (non destructive testing) Dye Penetrant, to check for cracks in a weldment. It's a 3 part, spray can, operation. Not real pricey, and you can get it at a welding supplier. One can is cleaner, you spray on let it sit per instruction. Then you spray 2nd can of penetrant, which is red in color. Let sit per instruct, then wipe off. Next is spray of developer, which is white in color. Any cracks remaining will show up as a fuzzy or distinct red line. We used on stainless and alloys that we couldn't mag particle test. But it works well on aluminum. Another trick I learned from a buddy who runs a sidecar Panhead at El Mirage and Bonneville, who was a aircraft mechanic. Heat your casting to 350 degrees in oven, I use an old gas grill, and hold it at that heat for 3-4 hours, then shut off grill and let cool. This works to stress relieve. Get temp sticks also from weld supplier. They are like a crayon, and they come in all degrees for checking temperature. As parts heat you rub the 350% stick on metal and when it gets to temp the stick will melt. Reduce heat and keep at that temp. I've found that Panhead cases that would keep cracking when I tried to weld using all know strategies, became weldable after this treatment. Also it really DOES help to go slow weld a little then stop and peen the weld with slag axe or whatever. I use an air chisel with a rounded pointed end to peen. I originally thought you just use peening on cast iron, but a guy who repair race car heads told me this. On weld wire I usually use 4043, but I've found if you're having hot short cracking problems, 4047 can help to stop cracking. This wire you may have to order and is more expensive, but I've also found it works. Hope you find this informative, and NO I do not take welding projects, I have 3 K's a KR, 2 XR750's, changes to my Bonneville Panhead, and 20 some other bikes of my own to get built. Ron L.