Engine up- and back-date rules?

[Knestis]

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

 

[ITANorm]

You may update / backdate entire assemblies as long as both vehicles are on the same line in the specs. Fairly simple.

Can you modify rods? No. Can you change cranks or valve springs? Yes, if you change the entire long block. The head is part of the long block (by accepted definition). Therefore, you can't put the dual valve spring head on the later block.

Technically, the crank must have all of the properties you describe; part #, dimensions, etc. must all be the same.

Is is legal to put in the forged crank? No.
Would you get caught? Probably never.
Why not do it anyway? It's Cheating.
Who'd know? You would - isn't that enough?

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Norm - #55 ITA, '86 MR2. [email protected]

Website: home.alltel.net/jberry

 

[Joe Harlan]

<font face=\"Verdana, Arial\" size=\"2\">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...</font>

Kirk, I am not going to even try to go into this one. I will give you a little back ground on what I know about the Z car issue you are talking about. The cars that came with the E31 head are all on te same spec line but they also came with either the 8mm or 9mm bolt rods which carry the same factory part number. In 1973 the same car came with an E88 head and crappy carbs but a better piston (displaces 3cc's more) We have been told we cannot mix the better piston with the better head even though we could make proper compression numbers. If I remember correctly this was protested many uears ago on the Z's maybe somebody would have a better memory than me about it.

 

[Bill Miller]

<font face=\"Verdana, Arial\" size=\"2\">Originally posted by Knestis: 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.</font>

Kirk,

I assume you're talking about using an OBD I head on an OBD II bottom end. Given that, as you said, you know the answer. The ITCS expressly calls out an engine long block as an example of a 'complete assembly', for the purpose of update/backdate.

If you can show that the early OBD II motors came w/ the dual valve spring head, or the late OBD I motors came w/ the different pistons/lighter rods, I'd say you're in the clear. Or, if you can show that the double-spring head is what's available now, and is what the dealer offers for sale, if you need a head (essentially a supercede). Same would go for the pistons/rods.

Does present an interesting situation though. Even if the head or pistons/rods are what's available, are you allowed to 'create' a motor that didn't exist? If you want to upgrade to the newer rods/pistons, would you be required to update to the newer head?

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