I had a heat riser valve stick shut on my Charger, and in the process of trying to free it up the valve shoaft broke off at one end. Since driving in cold temps was not a real issue, I plugged the shaft holes in the manfilod with a bolt, I recall I found a brass bolt and nut 1/4 diameter by about 3 - 3 1/2 inches or so in length and used a couple washers to help seal the holes. Its not the perfect solution but the brass doesnt rust away like an iron bolt, I can remove it easily should I ever really want to fix the thing and it very effectively sealed the problem/ Mikey 62 Crown Coupe