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7042240 Upper Main Bleed Question

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Rhett:
I'm doing a 7042240 from a Buick 455, and I'm at the point where I'm measuring and re-sizing the bleeds, etc...

I"ve found that the upper main air bleed in the body is TINY from the factory - .016! ....Cliff's book says to re-size to .070.... thats alot of drilling! The lower main is already at .070

Before I hog this thing out that much, is there something I'm missing? This is an idle air bypass carb, if that makes a difference.

Thanks, Rhett

Rhett:
Correction - it's the lower mains - the uppers are in the airhorn.

Rhett:
uppers are.070

omaha:
      Not sure, a bit confused.... Sometimes you can get confused easy because of all the airbleeds on all of the various year carbs. Main airbleeds, Idle airbleeds  upper and lower, single main air bleed carbs. Secondary airbleeds air bypass holes. That is why I had to read the book about 6 times just so I could remember. (LOL). I like the pictures in the book.  It really helps.

What did you measure that had the .016 measure, the upper idle bleed?

Rhett:
Ha! You and me both, brother!

These are the main air bleads - the upper is in the airhorn and is sized at .070 - no problems there. The lower is in the body, in line with the same passage and set back in a round recess in a round brass insert. The thing has the tiniest passage I've ever seen: .016 which is like a #78 bit - we're talking human hair sized.

The carb ran really well with the passage that small, I'm hesitant to drill it out if it's going to significantly change the performance chararistics of the carb....

But until I get a defininative opinion, I'm stuck and can't get this thing back together. 

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