On Tue, 20 Jan 2009 11:36:31 -0800 (PST), "
wrote:

On Jan 20, 6:50*am, Stealth Pilot
wrote:

I thought the valves could also stay where they are.
I also think that the exhaust duct can stay where it is.

I think that it is possible to substantially improve the exhaust
finning without changing the external dimensions much at all.
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My goal is to DOUBLE the amount of waste heat the head can handle.
Which means I need between 3x and 4x the AREA of the existing fins.

Examining a Lyncoming or Continental shows how they did it, although
there's no way I can emulate their fin 'density.'

Playing with a Corvair head shows how they did it... and did it using
a method which I CAN emulate.

the corvair head in leon's link shows me in the little marks from
casting that the head is cast into a multipart steel die.
I believe for short runs of castings these could be bolted together
with machined parts in mild steel and a silicon spray type release
agent used. Foseco make the release agent I have in mind.

But I've found it impossible to
maintain the bank-to-bank symmetry that makes the VW such a treat.

I would have thought that you design one head and mirror image it for
the others. that is how the symmetry is achieved.

If you are interested in this project I suggest you begin with a
junked late-model head. Cut it in half. Remove the rocker arm
towers. Remove the exhaust-stack studs.

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


Using modeling clay, move the exhaust stack to about the present
position of the existing push-rod tube hole (ie, the one farthest from
where you have just cut). You may install a boss where ever needed to
secure the Corvair-style exhaust stack. Fortunately, Volkswagen
includes a formed exhaust gasket in their muffler-gasket kit which
lends itself to using the Corvair-type of exhaust stack.

so you are moving the exhaust from front and rear orientation to
downward.

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.


Now you can go back to extending/adding-on new fins. So far, I've
'discovered' about 96 square inches (!!) of fin area that it MAY be
possible to develop. But it is going to be one weird bit of pattern-
making. (Due to the fins, one portion of the pattern must be
withdrawn ninety degrees away from the other.) Right now I'm looking
at a FOUR-PART flask. ( Remember, I said 'looking at' -- not in love
with.) Even so, it's going to be more difficult than anything I've
ever cast before. Not just because of the casting, but because of the
machining that follows.

I've not done anything at all with the inlet.

One step at a time.

ok. our approaches differ in that the fins worry you so you are
concentrating on them. I think that they are a solvable problem.
my approach is to worry about them last because I can look to lycoming
and continental and pratt 'n whitney et al for the solution.

where do the plugs go in the combustion chamber roof and where do the
valves go?

do you keep the valves in a horizontal line and place the plugs
vertically above and below as the usual vw conversion does?
this keeps the existing underslung camshaft reasonably happy.

if you keep the valves in the existing position in the chamber roof
and redirect the inlet port to vertically above and the exhaust to
vertically below? what advantages does that give you?
note havent got to the fins yet.
what answers do your gut feel from years of experience tell us?

Stealth Pilot