VWs

On Jan 30, 8:24 pm, wrote:

Are there non-stock cylinder heads, then?

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Yes there are, as a matter of fact. There are a number of after-
market heads intended for the HOT-ROD market, designed specifically to
deal with the CRACKING problem. They do this by casting the
combustion chamber almost half an inch THICKER. Unfortunately, this
results in LESS fin-area than before, which makes these heads even
LESS useful for flying VW conversions than the stock heads.
Enormously popular, of course :-)

So why didn't they address the REAL problem of inadequate fin area?
Because that would increase either the cost or the SIZE of the
cylinder heads.

Increase the physical size of the heads and they won't fit the stock
shrouding, meaning you'll be forced to modify virtually everything
that attaches to the heads -- upper (and lower) shrouding, intake &
exhaust manifolding... by which time the heads will be too expensive
for the Kiddie Trade, which is what they were designed for to begin
with.

Or, you can cast the heads as a block and MACHINE the fins so as to
give more fin area. Unfortunately, when you do so you run into the
same problem of high cost.

As for flying VW's and those of us who have forty or more years of
working with them, we have tried welding on additional fin-area, the
so-called 'Fat Fin' modification -- which DOES work... if you're
willing to devote lotsa money & time to it. Or you can read about
various experiments with liquid-cooled heads -- which also works... if
you can afford the radiator(s), pump(s), plumbing and WEIGHT that goes
with it.

But do all that you run into a very real -- but subtle -- limitation,
in that the BEARING AREA of the VW rods & crank was simply not
designed for LONG-TERM RELIABILITY at high levels of output. And
there is no work-around for that particular problem, although full-
flow oil filtration and the mods to the lubrication system -- that
were developed starting in the late 1950's -- provides for some
improvement (ie, the HVX mods).

Which leaves you with PSRU's -- torque multipliers -- which, in
theory, should allow you to operate the engine at higher rpm without
exceeding the inherent limitations of the crank & rods. But that's
only true if you address the cooling problems in a realistic fashion.

Put all that together and you'll have the equivalent of Rotax 912...
and for about the same price (!!) ...but at significantly more weight.

Don't take my word for any of this. Hit the books. Build some
engines. THINK FOR YOURSELF. Get stuck into it, you're only about
four years and maybe ten thousand dollars away from REALLY knowing
about VW conversions. Of course, once you arrive there no one will
believe you anyway :-) People believe what they WANT to be true. And
there are plenty of hucksters out there eager to prey upon that
ignorance.

After eight or ten years of fumbling around you're going to have to
decide if you want to spend all of your time tinkering with engines or
building an airframe that will probably never fly. Of course, those
things reflect the social aspect of homebuilding... which today makes
up about 99% of ALL homebuilt activities.

If on the off chance you're actually interested in FLYING then simply
follow the well-trodden path to a VP-1 or Teenie Two, bang it out --
keeping it as light as possible -- stick a STOCK 1600VW on the nose...
and go fly. You don't absolutely need to jump through all the FAA's
hoops -- there's no traffic cops in the sky. You will have divorced
yourself from the SOCIAL aspects of aviation more than the legal, but
if your primary interest is FLYING you will find it's an itch that's
pretty easy to scratch.

-R.S.Hoover




Since this heating problem has been known since the fifties it seems
like somebody would have come up with some heads (and jugs) that have
a lot more fin area. Like a Corvair -- or an aero engine. I've seen
two european companies that seem to be trying to address the heating
limitations of VWs that way.

I'm not even thinking here of somebody wanting to do an aero
conversion, but, since the aftermarket for VW keeps on going and going
that somebody doing racing or dunebuggies or just new or rebuilts for
VWs would have done such a head. I've looked on sites like
aircooled.net before I ever posted here but did not se