Black carbon at bottom of cooling jacket

[LSS&B]

1970 318LA. Pulled block cooling plug on right side to drain. On right side, I could not get a screwdriver through this black material that looks like hardened carbon. Had to use a long drill bit to open port. Scraped off this material. Looks black instead of rust colored.
Is this evidence of a cracked block?
Low vacuum and race cam in engine.
Poor gas mileage and coolant leaks.
Brown sealant in coolant
Cold engine passes 15psi cooling system pressure test.
Thanks, Ben

 

[khryslerkid]

More than likely it's just a byproduct of rust. You mentioned carbon and it's a byproduct of steel.

 

[pnora]

Could be core sand from when it was casted.

 

[moparedtn]

Rust when entirely submerged in water is black; it is when it is exposed to air that it turns brown/orange.

 

[khryslerkid]

Rust when entirely submerged in water is black; it is when it is exposed to air that it turns brown/orange.

You'll see plenty of black water when flushing a sprinkler system! I used to work maintenance at a hospital.

 

[LSS&B]

More than likely it's just a byproduct of rust. You mentioned carbon and it's a byproduct of steel.

Could be core sand from when it was casted.

Rust when entirely submerged in water is black; it is when it is exposed to air that it turns brown/orange.

Thanks all!
I plan to sell the 318 and I don't want to sell anyone a cracked block motor.
No cracks in the lifter valley which is where I usually see them on 318. Also, have looked long and hard at heads, no cracks, should be OK to sell.
I plan to install a carbureted 5.9 in it's place.

 

[moparedtn]

You'll see plenty of black water when flushing a sprinkler system! I used to work maintenance at a hospital.

40+ year fire sprinkler guy here, remember....

 

[khryslerkid]

View attachment 1811338
40+ year fire sprinkler guy here, remember....

Why do ya think I brought it up?