were is the hole if thru the head bolt you can run a brass liner a tube that gets push in and then broach in or if just EX gas you can weld nickel or use brazing filler rod or if it is in water you could weld or plug with i pipe plug if there is any room to drill/tap if you grinded thru then there are junk the cast may be to thin to do any thing to and make it very hard to weld