As for the SECOND point you've raised (although not the 2nd in
sequence), in which you said....

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On Jan 5, 5:33*am, Stealth Pilot
wrote:

btw why do you see building an engine as impossible? ...as opposed to
assembling one?

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One of the most difficult aspects of wrenching is convincing the
Average Joe that being able to ASSEMBLE an engine, as in, "Insert Tab
A Into Slot B..." is a very good first step in learning how to push-up
a tombstone, when that engine is powering an airplane.

The fact that a part FITS has very little to do with proper
assembly. (Simply select a batch of parts that are on the LONG side
of spec and everything will go together like a German toy.) It will
even Start. It even RUNS. But with those kind of specs the poor
thing is already about half way to being worn out. Seriously. Some
specs on the VW engine are pretty wide. As in PRETTY W I D E. Side
clearance on the rods... where the big-end fits the crankshaft... are .
010mm to .040mm... with a wear limit all the way out to .070mm fer
crysakes! The tricky bit here, as in several other critical 'fits' on
the VW engine, is that big-end side-clearance is also a factor in your
OIL PRESSURE, and for that reason what you want to shoot for is the
SMALLEST allowable clearance, or .010mm ( ie, about four thou ).
Symmetry also plays a role here, and shell-type bearings such as used
on the big-end of VW rods are never symmetrical... they do not form a
perfect circle. YOU must see to that, by 'releaving' the torqued
tension in the big-end. How? By hitting it with a hammer! (Okay,
okay, so we just tap it... and not with just any hammer, but with a
soft-faced hammer having a weight of a quarter-pound or less. And how
do you tell that you've releaved the bearing? You hold it out
horizontally then let it DROP.. under its own weight. It should take
about THREE SECONDS to fall to a purely vertical position. Sounds
kinda iffy, eh? Well, it is. So just make sure that ALL FOUR of your
rods have EXACTLY the SAME 'drop-time' and the engine will run
sweet... assuming you haven't shot it in the foot somewhere else along
the twisty path of Crankshaft mantling.

The problem here, and the reason I spend a lot of time screaming at
the newbies, is they have exactly ONE ENGINE'S-WORTH OF PARTS from
which to assemble an engine. And Reality simply don't work that way.
Oh, he'll end up with an engine. And the thing will even run. But
it won't run as good as it should; it won't be as efficient as it
could be. (I've had to sort through as many as EIGHT SETS OF RODS to
find four that satisfied ALL of the specs. And there's quite a few.
Interestingly, a lot of those specs are BEST checked by touch ( or by
FEEL, if you will). I can SHOW those things to a Newbie but since
he's only got ONE SET of parts to play with, it will be a waste of
time and effort. Odds are, he'll just slap the thing together and
hope for the best.

The answer to your questions is really very simple and has to do with
what the assembler must do when they're one engines-worth of parts
does NOT fit or does NOT run. Because you can spend some of the best
years of your life shipping junk parts back & forth until your
patience wears out along with your warranty.

-Bob