Crack in bottom of cylinder bore

[PseudoSport]

I’m working on refreshing my friends stroker engine that’s been sitting on a stand for 5 years. We tore it all down to, cleaned it up, and honed the cylinders with a ball hone. After a final cleaning we noticed that 2 cylinders had cracks at the bottom along a casting parting line. The crack stops when it gets to thicker metal below the lifters. It doesn’t go into a coolant passage and is 1” long. The block is a Renix that’s been bored .060 over. Walls were sonic check before the overbore to make sure they were thick enough. Has anyone else seen this?

[6TIME]

I had a 93' HO 4.0 block with about 200k on it do that (1/2' long hairline crack )slightly higher up where #'s 3-4 were siamesed. It acted like a blown HG once warm. Milled head and new HG, fired it up.... Blew the coolant out the radiator when warm again?? Tore it down and found a tiny line above the piston at BDC, looked like a piece of lint on the cylinder. Took a pick tool and scraped at it, sure enough it was a crack in #3. Odd for sure.

[IH 392]

Magnaflux it, if it is below the water jacket and the lifter boss drill the end of it to stop the crack.

[Russ Pottenger]

Magnaflux it, if it is below the water jacket and the lifter boss drill the end of it to stop the crack.

It's a $100.00 Jeep block not a 15k Lamborghini block.

If you want to mag and pressure test it that's fine, but the upside of trying to repair it compared to the downside
of havin water in your oil later isn't worth it.

My .02

[I6FAN]

What's up with the recess where the cylinder bore meets the block and the "scallops"? Back wall looks extremely "grainy"; probably full of porosity. I would get another one I think this is a bad casting.

[Cheromaniac]

Magnaflux it, if it is below the water jacket and the lifter boss drill the end of it to stop the crack.

Even if the crack is below the water jacket now, there's a risk the crack will extend higher after a few heat cycles so I'd scrap that block and start over. It seems the 0.060" overbore found the limit of that block.