<VV> Carburettor question(s)

[Sethracer at aol.com]

In a message dated 6/25/2009 12:06:28 P.M. Pacific Daylight Time,  
david.neale3 at ntlworld.com writes:

Would  one of you knowledgeable people please advise me regarding just 
how that  needle seats; and what effect one might experience if the 
needles are  missing?


Gravity seats the needles. There is a passage from the side of the float  
bowl to the area under the high-speed enrichment needle. The available flow 
is  metered with a pushed-in restrictor on the side of the float bowl. The 
needle  sits on the seat keeping fuel from flowing. The area above the needle 
is exposed  to vacuum at the tips and above the cluster, modified a bit by a 
few air bleeds.  As the vacuum at the cluster increases - only increased 
volume of flow does  this, vacuum at idle doesn't count, because it is not 
available to the cluster -  that vacuum pulls the needle off the sat allowing 
fuel to be pulled past the  sides and into the engine feeding air stream, 
enriching the mixture. If you  just pulled the needles out, that would richen 
the regular mixture up, sort of  like increasing the jet size a bunch. If you 
plug them, you would have  little mixture effect except under a high load. 
When I re-locate jets for  the racers, I move them around to the point on 
the carb where the restrictor  once lived. That new jet location is extended 
through to the hole below the  cluster. The original jet location and the 
well where the high-speed enrichment  once lived are plugged. The jetting in 
the carb must compensate for that,  because the factory's high-speed 
enrichment circuit is gone. I think if you just  pulled out existing needles, the car 
would get lousy gas mileage and fail an  emissions test. 



Seth  Emerson

C's the Day! - Corvair, Camaro,  Corvette




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