Subject: [alfa] head-porting at home

[RonHorowitz <RonHorowitz@xxxxxxxxxxxxxx>]

Subject: [alfa] head-porting at home

 >Once the current engine is out, I was planning to take to it with a die
grinder, and cut whacking great chunks out of the ports, closely following
the instructions in Jim >Kartalamakis' "How to Power-Tune Alfa Romeo
Twin-Cam Engines".

Bad.

>Lately, however, I've been having a few doubts.

Good.

>Does anyone have actual, verified, preferably tested experience of the
Kartalamakis instructions and measurements?

I've never bothered to measure a Kartalamakis designed port, and I hate to
be a naysayer, but I can tell you from inspection that regardless of the
relative merits of his other advice, Kartalamakis' port geometry is NFG.

 In porting, what you really want is a "steamlined" flow pattern with the
gasses travelling at the maximum possible velocity. If you have a bad
geometry, you can't get the gasses going very fast before the flow gets
excessively turbulent and the CFM falls off. The Kartamalakis geometry
isn't particularly streamlined, it just slows the gasses down a lot. That
may give you higher CFM, but not high energy, and it won't give you the
best integral of power vs. RPM, nevermind throttle response, charge
turbulence, and all of that,

Think of it this way, for you to have maximum "inertial ramming," first you
have to have maximum inertia. Increasing the port radius increases the port
area by the square of the radius, so the (mv**2)/2 term falls with the
fourth power of the radius. Mindlessly "hogging out" a port without resort
to flow bench CFM and velocity testing and / or a fairly accurate CFD model
is foolishness.
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