Quote:
Originally Posted by zrayr
What is the purpose, if any, of this cavity in the main carb body casting ? . . .
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When making a casting, thick areas generate shrinkage problems. The casting is symmetrical about the float chamber. On one side is the hole for the accelerator pump - only one needed so nothing on the opposite side would create a large thick area. To deal with this, the designer then cored out the area to reduce the amount of metal being poured. I can understand his thinking when designing the casting to keep the float chamber symmetrical so just make this an unused cavity.
Like Rick said, some VW guys mill the wall out to get a larger float chamber. Since the 2-3lb fuel pressure doesn't flow real fast, some drag racers were running out of fuel on their pass. This helps that problem.
Really a non-issue on our cars - unless maybe you're drag racing a set of Webers.
Paul