[Dave in MN]

I would go with Tom Wesenberg and Brent's suggestion. Try the JB Weld first. I always use JB Weld first on the type of crack you describe. I Magnaflux the crack, mark its path with a permanent marker, drill a small hole (3/32") at both ends of the crack, use a Dremmel tool with a very thin cut-off blade to create a very shallow (1/32") deep channel exactly over the crack and then fill (actually mound it up over the channel) with slow set JB Weld. Optional step: The following process has worked exceptionally well for me. After about 2-5 hours of curing at room temperature, I lightly tap on the JB weld with a very small hammer to force the epoxy into the actual crack. Why the wide variance of time for the tapping...it depends on the setting of the epoxy. I start tapping as soon as the epoxy starts to set. I do not tap on it if it has stiffened significantly.
The extra surface area of the shallow channel allows the JB Weld to bond well to the repair area. After the JB Weld sets up over night, I remove the excess with a course file and finish it with sand paper. Removing the excess leaves only the epoxy in the shallow groove. The difference in surface texture can be masked by taking 80-180 grit sand paper, placing it over the repair and tapping it with a small hammer to create a surface to match the cast iron. After painting, the repair is not noticeable. I have been using this repair for the past 10 years and have not had one fail yet. I install "Lock Stitch" repairs in other areas of the block but often find the metal very thin in the area you describe making it a very precise and tedious process. Given the success of the JB Weld, I consider stitching an over-kill for this particular repair.
Good luck with your repair.
Dave in MN
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