This head has over 100,000 miles on it with the original Exhaust threads. To keep the threads from blowing out the nut is screwed in first without the pipe (with a bit of silicone on the threads). Put in a couple washers before you screw in the nut. A sleeve is added to the pipe O.D. so it fits inside the nut and a loop is added for the spring - both are brazed on with phosphorus bronze brazing rod (higher temp than regular brazing rod). A little silicone is smeared on the pipe O.D. where it fits into the nut to get an air tight seal. Then you just retighten the nuts after a couple heat cycles and leave the nuts in. The vibration no longer pounds out the Exhaust threads because the pipes are not fixed to the nuts (the flanges on the pipes are removed and the pipes are held in with the springs). This is a trouble and worry free arrangement and it beats the hell out of having your alum threads getting pounded out.
