DIRTY ROTTEN #$%^&*&^%$# My blocks cracked! XK-19

[Bad Ass Boat]

This is a weird one. When I bought my boat I checked the outside of the block and all over and there were no cracks what so ever.No freeze plugs pushed out. I got it home and checked to see if there was any water in the manifolds or block and everything was drained and bone dry. 0 milk shake in the crank case! I went woopee!!!!! Then I pulled the engine down to rebuild it and To my surprise there was a big crack in the inside of the valley right underneath no 3 cyl I mean it was pushed out! This is weird no millshake and no water but the block is cracked and pushed out under no 3 cyl. A freind of mine said it was never ran after it cracked. Most engines Ive seen they crack on the out side of the block. I conntacted a machine shop and he has seen plenty of these on chevs. There goes my matching number block for my 19 BUMMER!ARRRRRRRRG! Any ideas guys?

[Wood Commander]

May be a totally different situation, but.......

I had an intake manifold on a Hercules/Chris Craft flathead, six cylinder 130 hp "M" series engine crack even though the engine was drained of water.

The passageway that cracked was plugged shut tight with silt and contamination. The blockage remained wet, and any antifreeze that may have been run through the engine could not get into this area due to the blockage. So the wet blockage material froze and cracked the part even though the rest of the engine was fine.

I've also noticed on some small block Chevy engine cores that I have torn down, that when I removed the drain plugs at the bottom of the block right above the oil pan gasket rail, they were totally plugged and no coolant ran out. This is something that needs to be checked after a core comes back from hot- tanking at the machine shop to make sure the proceedure clears out all of the water passages.
If I don't totally rebuild any of these engines and try to run them as is, I'll probably try to pour some acid like you use to clean bricks with (is that muratic acid?, it foams and bubbles on most surfaces and requires a baking soda rinse to neutralize it) down the water passages higher up on the block and see if the acid will clean the passages out well enough to run the engine.
I'd be afraid to use an engine if you can't have flow at the lower block drain holes.

So I wonder if a blockage of wet sludge trapped in your block may have done the dirty deed?

[Bad Ass Boat]

This is an interesting angle I have never considered. I know these blocks are very rusty people dont know to drain them after they put them in the drink. Some dont care. But that makes sense that you could have some blockage with some moisture in the crevices. I know a lot of times when I have drained blocks on customers boat nothing comes out I have to pull the peckcock out and run some wire up there to dislodge the rust. Two things must have happend, sombody didnt winterize it and let it set then drained it in the spring and never run it or what you have described. One of the exhaust manifolds had a crack underneath but the other one did not this is really a weird one.