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My take on old webers vs new


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As far as the lore of old webers being better than new here is my take. The skill required to properly set up a set of carbs of any brand is a lifetime of trial and error and lessons learned plus the basic knowledge of how a carburetor and all of its given circuits and components work together combined with the basic requirements of a given motor. The number of truly skilled people able to PROPERLY set up a set of carbs has gone from probably a few hundred in the 70's to a steadily lower number as the decades past and those guys have retired or died. So the chances of someone buying a set of webers in the 90's and having someone properly set them up was very low and got steadily lower as years passed. The number of shops with a full range of idle and main jets, air corrector jets, accelerator pump jets, emulsion tubes, chokes, venturi's, etc. is very low. Plus knowing how each one interacts with each other.  Most likely they bought a few richer or leaner jets it ran OK and called it a day. 
   The emulsion tubes for example. The numbering system for them refers only to order they were created. For example a f2 emulsion tube is the second one ever created and a f5 is the fifth. It has nothing to do with how they act. They were created as Weber supplied carburetors for different production cars and race cars and developed new tubes to correctly tune a given motor. So the only way to know what a f2 does vs a f5 is to have tested it or know from someone else in the field who has. 
  The exact same thing exists with Weber idle jets. A 45 f6 idle jet is richer than a 45 f9 but a 45 f8 is leaner than the f9. And this is at some point of the delivery curve of that jet not just plain leaner or richer period but each act different from each other as the flow through them increases. It's crazy to think of all the possible different combinations. Each different idle jet f number was created to solve someone's problem in their motor fueling. 

So I will bet that most of this lore comes from buying old carbs that were at some point set up pretty well for the car they were on and someone bought that set for their similar car and they worked great compared to their friend who is struggling with their new set. 

 I would prefer a new 40 dcoe 151 over an old 40 dcoe 18 any day. Mainly because they have an air bleed to correct for the difference in flow between the barrels of a single carb.  Say the front throat is flowing 3 and the second is 3.5. You can crack open the air bleed on the low barrel and bring it up to match the 3.5 of the higher flowing butterfly. I have also had great experiences with the 45 dcoe 152G vs the standard 45 dcoe 9. 
the 152g has 4 progression holes on the idle circuit vs 3 in the standard 45 and on a 3.0L big cam motor this carbs works great. 

That all I have to say. 

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