i have the same problem right now with a 39 head,,and solved it the same way i did before.Using the existing thread i turn in a new nipple, coated with coppa-slip,its copperpaste that allows tightened bolts to loosen up easily, used in refineries and so on.I turn in the nipple using the manifoldnut and bushing.When its really tight i take off the nut, and start building up the tornaway part using mig welding.I try to avoid direct contact with the nipple as much as possible,aiming at the head material,very short moments, and use low amperage.The coppaslip more or less prevents welding the nipple itself.After grinding the irregularities i drill a new hole for the pin,going thru the bushing of course,put in the pin from the inside, and using high amp.(150) i spotweld it on the outside.It looks good,keeps the nipple in its place,and when the nipple accidently gets welded to the head, bad luck,next time you need to replace it(for what, and in how many years?)Break it out, and do the same again.
I do the same with partial torn out headbolts.
I know this works fine for me, but if you have the tools and experience maybe its your solution as well
best thing is to use a dremel for bringing back the pinhole instead of drilling due to hard welding material,After rebuilding the gap with low amp, you should cover it all wih high amp welding,this makes it melt all nicely, and no danger of adhering to the nipple
[This message has been edited by rein (edited 23 June 2000).]