<VV> Re: LM carbs

[NicolCS at aol.com]

I've heard and read over the years that "Smog carburetors run lean".  I don't 
believe this is true at mid-range cruise and it's certaily untrue at idle.  
While the AIR system controls HC partly through limiting carburetor excursions 
into the excessively rich range, engineers were also concerned about excessive 
NOx emissions - which go ballistic at lean mixtures and high combustion 
temperatures. To manage the two-headed beast, so called "Smog" carburetors have a 
two-stage emulsion system that is more accurate than the earlier carburetors 
and this limits unwanted mixture excursions both on the rich and lean side of 
"correct".  They are more accurate, not "lean".  Of course smog carburetors 
don't have the power enrichment circuit but remember, power enrichment, uh, makes 
more power and thus more heat.  I don't think I'd blame overheating on a more 
accurate mixture and lower total power production.  Of course, a matched pair 
of carburetors is best.
Craig Nicol