small block casting numbers

[ir3333]

what's your interpretation of the last 4 block casting numbers below the
drivers side head under the exhaust?
i.e.....340-2---340-3,----340-4---318-2---318-3 etc?

 

[j par]

The casting mold #

 

[Lelo Dart]

cubic inches of motor - # of times used with the same mold. 318-4 , motor is the 4th one from that mold.

 

[Alaskan_TA]

The number after the - is the core revision number.

Anytime a mold was corrected for core shift the number went up.

 

[ir3333]

i have heard this too,as the moulds wear the core moulds continue to need adjustment,and
this number indicates that number of revisions ..the mould is eventually worn out / replaced.
..so a 318 -2 may be a better block than a 318 -9?
I have seen them priced accordingly used.

 

[Alaskan_TA]

The better block would be the first one out of the mold (if it had no flaws) or the first one after it was retooled each time. (again, if there were no flaws)

Buy a block after checked for flaws, cracks, machining errors, etc. not for numbers cast in the side.

 

[rigger3006]

the 360 i got from junkyard had no mold number after 360, would that mean it was 1st, or possibly ''flawless'' lol?