[alfa] Re: Alfa head porting

[White Anthony <anthony.white@xxxxxxxxxxxxxx>]

In the midst of last week's head porting debate (many thanks to Eric and Ron, 
from whom much was learnt), another digester wrote me off-list, with the 
following advice, received from an ostensible Alfa-engine-guru:

"The cardinal sin is to remove the air-splitter groove in the intake ports.  
If you look carefully at the AR inlet port you will see a pair of ribs cast 
into the top of the port.  These extend from close to the port face to 
almost the inlet valve plenum.  These are designed to split the air flow 
and ensure the air swirls to either side of the inlet valve.  Remove this 
splitter and the air flow drops dramatically and dams up against the inlet 
valve head.  Result is much less air flow."  

So I pulled my spare head, and mostly stripped it over the weekend.  Looking 
for these ribs, I found myself a little confused.  This is a late seventies Alfetta 
2L head.  I found not two but three ribs, cast in the bottom of the port, not the 
top, and they're also cast into the exhaust port -- where there's no need to split 
the airflow around a valve.  They run parallel to each other, which it wouldn't 
seem would have much of a splitting effect.  Furthermore, they are pretty poorly 
cast (inconsistent, rough) and must be less than 0.25mm high.  

Does anyone else have any knowledge of these ribs, their design function or 
effectiveness?  Any thoughts?

Kind regards,
Anthony
Wellington, NZ
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