Anyone come across this before?!

Ive been stripping down my 1956 Aussie import and came across these embedded in the block?
Purely out of interest has anyone come across this before?
...and whilst Im here.....the engine (2litre) water jacket is half full of rubbish...sand and v hard deposits and is going to be sent to Coxs for machining.....

...is there any chemical that will dissolve the deposit and the brass water tubes...is it easy to remove and replace these?

Thank you

David
Suffolk

Never seen anything like that before, interesting though.

Is it blocking the rear water way?
Looks interesting

At least that core plug won’t rust !

With it being a series 1 2lt your best of going to series 1 forum or club.
Core plug is probably spot on.
Turners may be able to help they have the ones for later engines.
Or Dunsfold .
https://www.turnerengineering.co.uk...MI_ry71_nf6AIViKztCh043wrDEAQYAyABEgJnW_D_BwE