Carter BBS Slant 170cui idle problems

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Were that drill bit is sticking out is the bottom of the idle down Channel. Rather than pull that clean out plug. With Top of the carburetor still on air pressure applied at the bottom of that hole will reverse flush the entire Idle circuit

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1969 was the last year Carter gave us the specifications for the idle circuit. idle jet for your carb .033, Carter did use different specifications on Idle Jet depending on carb number and application. Idle restriction also called economizer .052 that's pretty much standard on all bbs's. The idle bleed .061 or .062 also pretty common.

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Second picture a paper clip is being used to verify cross Channel and idle restriction is open, a welder's dip cleaner would be a better tool. Third picture is a visual of where cross-channel enters the idle Jet well just to the left of that red dot.
 
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Personal preference rather than put that aluminum clean out plug back in there. A screw of the right dimensions can be just screwed in that same hole with just a finger and a thumb, no Taps and dies and wrenches necessary. Finger tight good enough

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That opening is about.128,center of screw close to that outside screw threads just a little bit bigger

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Where that arrow is pointing, can you tell us about that. Does it go to your exhaust manifold. Where is your PVC valve connection.
 
That red straw is the idle down path to the adjustment screw, if that gasket is flipped the wrong way it will block the idle Channel completely

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Above that white spot is a threaded entry port for heated air from the exhaust manifold, travels around. Half moon shape, at the left of the white. There should be an entry point into the Airstream of the carburetor. It's almost visible that little black spot. It's possible that there was a restriction bushing in that hole at one time. That fell out a long time ago, possible vacuum leak
 
Something to be aware of Carter listed two different flange gaskets part number 1a-153 export and 1a-315 every thing else. PVC valve was in two different places depending on application
 
First picture is threaded port for heated air 1969 and export, in 1970 that port became the the PVC valve port in usa. Yours remain the same. Second picture is it good guess.. Should be where your PVC Port is opposite side of the carburetor. The gasket should have a round hole in it with a matching hole in the intake manifold the wrong basket or no hole in manifold can be made to work by notching the sidewall that gasket
 
Red dots and green dots different entry points for PCV valves and on right separate hole on left built-to base a notch. On left by Black Arrow newer Idle circuitry, on right Black Arrow older idel circuitry
 
Intake manifold designs one with hole one without, from what I can tell you should have a hole.

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First picture manifold no hole different design carburetor different gasket. Next two pictures manifold has holes, different design carburetor, different gaskets. When the carburetor is designed it's assumed certain amount of air flow from the PVC valve. Idle Circuit is designed around this expected air flow. No airflow from wrong gasket or too much airflow from faulty PVC valve, will upset idle circuit
 
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