Thread: crack in flathead engine

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I second the advice of firebird77clone. The only way to "maybe" get a good weld on cast iron is to heat the block in an oven and weld it hot and then anneal it and slowly cool it. One other very chancy method is to sleeve it and braze the top edge to seal it and then bore out the sleeve to the size of the other cylinders. Do you mean a 1/16 wide crack all the way down in the bore? If so that is probably not repairable. The chance of you patching this yourself is less than 1% in my opinion. I recall trying this on a Model-A block, getting a nice weld and then when it cooled it went tinkle, tinkle and cracked worse than before because I had no way to anneal the weld. Even with professional help and an experienced shop with annealing facilities I would still say the chance of a successful patch is only about 50%. Take it to a shop which has experience in such repair and cross your fingers and maybe you will get lucky?

Don Shillady
Retired Scientist.teen rodder