I know that this will appropriately degenerate into a philosophical argument but I'm at a place where I'm starting to think about building a "proper" IT engine. My most resent questions were triggered to some degree by a question elsewhere about machining rods to accommodate larger bolts, that seem to have been OE in some versions of the engine in question...

The book talks about updating/backdating "complete assemlies" and specifically refers to "engine long block" as an example. To put this in context, there are some pieces available in the MkIII generation of ITB VW Golfs ('93-97 in the ITCS) that are considered better than others, with substantive changes happening more-or-less with the switch from OBDI to OBDII systems somewhere in the middle of that span.

My understanding of this situation is that I should be able to use the dual valve spring head from the earlier sub-generation, sandwiched between the OBDII FI stuff and a later bottom end with better pistons and lighter rods.

Any concerns with this? I didn't think so.

Now, what if earlier engines came with a forged crank? What standard would have to be applied for that to be OK - not necessarily under the up-/back-date clause: If it had the same P/N as the later cast versions? If it were merely the same dimension?

The rules NERD in me thinks he knows the answer but I'd still be interested in opinions.

K