Hi again.
Another way to approach this problem is to see if there are any “unused” threads left in the bottom of the threaded hole in the block, ie. you may be able to use a longer bolt….Check the depth of the hole and compare that distance with the amount of bolt that projects beyond the exhaust flange and gasket. Get a new bolt and cut it to the maximum possible length, but of course ensure that it cannot “bottom” in the hole. Also ensure that there is no debris in the bottom of the hole. There is often a surprising amount! Whilst on the subject, next time you have the barrel off also check that the threaded holes for the cylinder holding-down bolts are also thoroughly cleaned out, as they also seem to accumulate debris. Yet another approach, ie. bodge, if you have a set of adjustable split dies, is to make a new bolt that is “fat on the threads”, ie. a bit oversize, but don’t overdo it as if too tight it could crack the cast iron if forced in. Make sure that it can be screwed in without resorting to much more than fingers!
