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Got an lm7 block machined and I found these divots on the head mating surface. Attempting my first build so not an expert but I do assume that it’s probably not going to be a good idea to continue with this block. Any opinions appreciated.
When I was just out of high school@18 years old, and still knew everything (), before I ever worked in a shop, I once ported some individual aluminum intake manifolds for a Honda CB 500-4 motorcycle, a bike which, two years later, I eventually got running well enough so it ran under the national record ET for D/MB. Anyway, no matter how much I kept grinding and polishing, those damn little casting bubble divots kept reappearing. Finally, in frustration, I went to my dad, an old T&D maker. He laughed and told me I could keep grinding until I broke thru the aluminum, and they'd still be there! Then he splained!! Most any casting will exhibit those divots to one degree or another. Unless it is HIP'ed, which uses hydrogen (90%sure?) forced into a Hiperbaric chamber to help eliminate the voids. The C5R block is Hip'ed, and is, AFAIK, the strongest 4.125"bore block available. They were manufactured to be reliable to 900hp, much stronger than the LS7 block. They cost over $6,000 15-20 years ago.......
Last edited by grinder11; Jan 3, 2026 at 03:09 PM.
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Divots in head mating surface. 
), before I ever worked in a shop, I once ported some individual aluminum intake manifolds for a Honda CB 500-4 motorcycle, a bike which, two years later, I eventually got running well enough so it ran under the national record ET for D/MB. Anyway, no matter how much I kept grinding and polishing, those damn little casting bubble divots kept reappearing. Finally, in frustration, I went to my dad, an old T&D maker. He laughed and told me I could keep grinding until I broke thru the aluminum, and they'd still be there! Then he splained!! Most any casting will exhibit those divots to one degree or another. Unless it is HIP'ed, which uses hydrogen (90%sure?) forced into a Hiperbaric chamber to help eliminate the voids. The C5R block is Hip'ed, and is, AFAIK, the strongest 4.125"bore block available. They were manufactured to be reliable to 900hp, much stronger than the LS7 block. They cost over $6,000 15-20 years ago.......
