i presume i have a genuine cosworth 205 block with yb number stamped just above water pump.i also have 2 inj pinto 205 blocks.above the distributor hole on the cosworth block is stamped 2222 also on one of the pinto blocks,the other pinto block is stamped 3333.i was once told this related to the thickness of the cores is this correct.
thanks brian

 

it will say 205 under the exhaust manifold the 2222-3333 are the bore size tollerance for bores 1-4. the pistons come in the same grade numbers you can find the sizes in the Cosworth manuals.

 

Try here

https://passionford.com/forum/viewtopic.php?t=63056