Hello,
I wonder if these types of marks are normal on the block, this is just under the alternator.

Look at the RHS of this photo
A close up of the above

Thank you.

 

IMO it just looks like casting marks...Nothing to worry about.

 

They appear to be just "fissures" on the surface of the casting caused when the surface cooled more quickly than the material just below the surface. (excuse bad grammer - too many surfaces!) It's often difficult to get the mould hot enough to prevent this. Only likely to be a problem if the cooling was too rapid.
JohnD

 

Good, just what I wanted to hear, thanks again