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

(no need to raise to this bait. it isnt in presenile dementia mode)
---------------------------------------------------------

'sllright. Any msg from Down Under is assumed to be slightly fey
(notice the ASSUMPTION again)

But as a point of interest...

Casting aruminumm VW heads DOES require incantations and Black Art
babbelations to get one suitable for machining. But it would be well
worth your while, if you intend to fly behind a converted VW. Why?
Because the original heads are severely limited with regard to fin
surface-area, restricting their maximum SUSTAINABLE output. The heads
are NOT L & R but one size fits all, or L/R.

Thg reason for LIMITING the fin area is that the heads must fit under
the stock shrouding as used in vehicle engines. If you do not have
that limitation... if your cooling is due to RAM AIR and you are
building the plenum chamber yourself, you do not have that limitation
and my increase the fin area by a significant amount, allowing the
engine to produce a MUCH higher level of output under Standard Day
conditions.

Casting your own heads not only permits a higher level of output, it
allows you to ANGLE the roof of the chamber slightly, allowing the use
of larger than stock valves without having their center edges encroach
upon the spark plug, which is located slightly above the valve's
center-line.

By casting your own heads you may also modify the exhaust's OUTLET
PORT in the manner used by Porsche. Doing so will alleviate a host of
problems associated with the exhaust valves, the most common of which
is being forced to use valves having stems of small diameter,
precluding the use of large-diameter, sodium-filled stems.

Of course, you need to be a pretty good pattern-maker to begin with,
and have access to a pot of alloy of suitable temperature that has NOT
been in contact with steel or iron (ie, a silicon carbide pot, or a
steel pot lined with a ceramic coating.

Some years ago I EXPERIMENTED with VW head castings. To ensure the
proper alloy I simply used old, damaged heads as my donor metal. But
for the other details, as best I can recall I spent a lot of time
crying; dumping unsuccessful heads back into the pot, and wishing I'd
gone farther in seminary instead of deciding to Join the Navy and See
the World.

-R.S.Hoover