REFLECTOR: Running LOP

[Keith Hallsten]

No, "porting and polishing" is the process by which the air flow passages in
the heads (outside of the valves) are opened up for better breathing,
typically with a die grinder.  It requires that a flow bench be available so
that the changes to the cylinders all match.  It also requires some artistic
talent and a very clear idea of where the stresses in the head are, so that
the cylinder isn't weakened.

When Ly-Con built up my IO-540 I had them port and polish the new Lycoming
cylinders to get all six to breathe the same.  I wasn't really after more
power, I was really after the ability to run Lean of Peak.  While testing
the engine in the test cell, they also did a bit of witchcraft with reaming
the injectors to try to get the fuel distribution as well balanced as
possible.  The nominal 260-hp engine actually made about 293 hp at 2700 rpm
with my Custom Aircraft Parts 3-into-1 exhaust stacks installed.

Now if I can just finish up the plane and get it in the air!

Keith Hallsten, XLFG
 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of John Dibble
Sent: Wednesday, January 03, 2007 9:47 AM
To: Velocity Aircraft Owners and Builders list
Subject: Re: REFLECTOR: Running LOP

By porting, do you mean adjusting the size (opening) of the intake port to
each
cylinder?

John

michalk wrote:

>
>
> For an aircraft engine, I imagine the racer guys port their engines for
> optimum power.  I don't know if they port for even airflow though.  I
> would think they port for max HP from each cylinder, which may not be
even.
>
> John Dibble wrote:
> > How does one go about tuning a carbureted engine?
> >
> > John
> >
> > michalk wrote:
> >
> >
> >>  I would
> >>bet that well tuned carbureted motorcycle engines have very good
> >>distribution.
> >
> >
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