Block casting void near exhaust port?!

[GarethJ]

So I delved into a crack in my block this evening. Most likely split with rust/frost or a combination of the two.

Lots of cracks around the non water inlet side of the exhaust stub. Upon digging a bit, it looks like there originally might have been a void under here.

Just curious really, is this void here on purpose? A casting defect? Or has it been carved out by decades of corrosion?

If it is intentional, what's its purpose? I can't see that area being hollow doing very much for cooling...

I may try brazing some stainless plate over the lot but it's no great loss if it has to be binned

[headdownarseup]

As far as i'm led to believe it's there by design.
Silver Century blocks appear to have this same "void".

Correct me if i'm wrong, but its purpose is for cooling the exhaust gasses that are leaving the cylinder, as well as wicking away heat from the combustion process.


Now you can start to see why we're so intent on flushing out water jackets after use. Perhaps after looking at this,putting the motor away after a thorough drying may have been a good idea as well. Pools of water INSIDE the water jacket that are left to their own devices can cause no end of trouble like this.


Jon

[GarethJ]

After some more prodding since posting, I agree it's there on purpose.

I'm not sure about cooling exhaust gasses as the heat transfer would be minimal. Probably more about keeping as much water in the block as possible to cool the overall unit.

Anyway, I brazed it up to a fashion. There are some pinholes but hopefully they'll be small enough to not cause trouble. It's only a scrap/project block anyway.

I didn't let it crack, it came in a box of junk bits I bought.