After trying as many different methods of separating the head from block on my 59 Brum as I could think of, I finally did what was suggested a number of times,a very long time ago. Taking trusty hacksaw in hand I proceeded to cut through only as many of the offensive studs as was necessary to achieve departure of the accursed dissimilar metals. As luck(did I say luck) would have it the two centre studs and the front water pipe did not have to be cut through. The studs came out of the aluminum head readily enough ,though it seemed that the outside studs took a few more blows than inner ones. As for the remainder of the studs in the cylinder block we center drilled a hole through them and migwelded washers and 1/2 ” nuts to them and succeeded in removing all but 5 that broke off down the hole. I will try and enlarge the holes so that I can pick out remainder of metal in threads, of course very carefully. All in all I was quite pleased with the final outcome. Very minimal marring was done either to head or block from the hacksawing. Will take them to machine shop for skimming. I will have to make up new studs of course and would like to know thoughts on what kind of material I should be looking for. Also the head nuts I removed were acorn type nuts with no washers, looked good but not sure if correct or not. Once more any help is greatly appreciated.
And thank you to the many who have helped me get this far. Should be all done for the spring/summer riding season.
You could try a medium carbon nickel/chrome/molybdenum steel such as 817M40, (EN24 in old money), New World specs. are bound to be different again but for reference the composition of EN24 is:
C = 0.35 to 0.45%,
Si = 0.0.1 to 0.35%,
Mn = 0.45 to 0.70%,
Ni =1.3 to 1.8%,
Cr = 0.9 t0 1.4%
Mo =0.2 to 0.35%
It can be heat treated up to 100 tons/sq.in. tensile if desired although, in the UK at least, the EN24t version, (40tons tensile) as supplied is readily machineable and probably adequate for this purpose.
On the other hand a visit to a breakers yard should yield a plentiful supply of cylinder studs to modify.