Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

Quadrajet running lean after head and cam swap

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bcarlson78248:
When I replied with my phone it cut off the end of my message.

Question - What is DCR - is it the idle down channel restriction?
I measured the idle down channel and its about .051-.052, so it looks like I need to drill it out to .055 (my .050 drill bit fit loosely, but the .052 bit won't quite make it.)

Is there any trick to drilling the idle down channel larger?  The fittings appear to be made of brass and pressed into the carburetor.  If I drill them from the top I can't see where the filings go or how to ensure the filings are flushed out.

Thanks,

Bruce

77cruiser:
With the base off just blow the channels out with air. The channel is fairly large so it will clean out.

bcarlson78248:
I've continue to work on the carburetor and have these setting/specs so far. 

The only question I have now is whether I need to make any changes to open up the lower idle air bleed or reduce idle bypass air.   
Idle bypass air is larger than expected, but I've also converted to an electric choke. 

Idle air tube - opened to .038
DCR - opened up to .055
Upper idle air bleed - .052 stock (in air horn)
Lower idle air bleed - .0625 stock
Idle bypass air - stock was about .105 (larger than expected)
Mixture screw hole - opened up to .078
Plate holes - none
APT - currently 3 1/2 turns out
I also notched the secondary air flaps so that the fuel holes were exposed to the underside of the flaps.

Thanks,

Brucee

77cruiser:
Don't open the idle bleed, looks like you should be rich enough now.

Cliff Ruggles:
The upper idle airbleed is in the main casting just above the DCR's, not in the airhorn.  It's probably around .070".  No need to modify any airbleeds at this time.

The idle tubes are also fuel supply, not air.......Cliff

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