On Jan 21, 12:02*am, Stealth Pilot
wrote:

this is not an academic exercise for me. I will need just such an
engine for my Turbulent.
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Buncha other folks too.

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The problem with the thread bases and the
woodruff key in the crankshaft causing fatigue failures is *exactly*
why I havent proceeded with just a simple vw conversion.
I'd actually like to build a sorted out trouble free engine.
sourcing one of the aero intended forged cranks and building around it
seems an option.
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The answer to the Fractured Pulley Hub Problem is to simply put the
prop on the OTHER END of the crankshaft... as is done with all other
auto engine conversions you can think of .

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so you are moving the exhaust from front and rear orientation to
downward.
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YES! This appears to be the easiest modification to do, as well as
the one most likely to meet the requirements of the Home-built
community.

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what type of sparkplugs would need to be used for this engine and
where would they go?
this is critical because they need access clearance for servicing.
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The Volkswagen engine uses a Wedge-type combustion chamber with its
associated 'squish' areas. The spark plug will be located at about
the same location as resent, since this is the position of maximum
turbulence (which is needed for proper ignition). There is enough
'meat' in this area to allow room for a SECOND spark plug... but wedge-
type combustion chambers have shown no benefit from multiple points of
igntion until the diameter exceeds five inches or thereabouts. The
use of dual plugs in some modern automotive engines reflects their
extremely high COMPRESSION RATIO. Since that does not apply to a
converted VW, neither do the dual plugs. Indeed, the only reason for
providing ANY provision for dual ignition is to satisfy the Feel Good
legislation hurriedly passed (..1937? ) following the death of a
Congressman's son in an airplane having a single ignition system. (As
a point of interest, about 80% of ALL engine failures during that era
(ie, early 20's to late 1930's) were due to IGNITION failures.
Because of that, the US Navy REQUIRED their engines to be fitted with
TWO ignition systems. The joke here is that the problems which causes
all those failures had largely been ELIMINATED by the late 1930's [and
are totally absent today!]. Indeed, a modern automotive ignition
system is several order's-of-magnitude MORE RELIABLE than the typical
aviation magneto of the 21st century.)
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where do the plugs go in the combustion chamber roof and where do the
valves go?

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I donno. Where do they go on YOUR conversion? :-)

Actually, after spending several hours with heads last evening I may
have found a better system than the one I originally described.

In either case, it's a lot of work and I've got a few other things on
my plate at the moment.

-R.S. Hoover