numbers on screws

Looking at my carter stuff it would seem most slants got venturi cluster screw 101-569 . Bypass air bleed .063 and economiser .059. Some exceptions 78 mexico auto got 101-579 .067 air and .059 economiser, some 78 trucks got 101-639 ,067 air .055 economiser

Recent testing after using a whole can of carb cleaner, idle still lean curb idle and off idle transition. This with 101-639 venturi screw, .067 and .055 checked economiser with blunt end of no.54 drill bit -055, would not pass threw. Just using fingers cleaned hole with sharp end of same bit. Rust and crude came out no metal.Idle and off idle now much better.

Still using screw 101-639, the real fix was to enlarge the economiser to the same size as most other slants used. 101-569, .063 air and .059 economiser. Used no. 53 drill bit .059 to open up economser, this time a very small amount of metal came out. This made this screw the same size as 101-579, the mexico 78 autos got. The air bleed is still .067 as opposed to .063 but idle is just fine. The old carter drill charts says no 54 bit .055 is in area in square inches .00237 and no 53 bit .059 is in area in square inches .00274. That is 16 percent increase in area of hole

Carter used many different venturi cluster screws 101-569 .063 air .059 econ common on the slant 101-579 .067 air .059 econ 101-639 .067 air .055 econ 101-687 .063 air ..055 econ 101-593 .059 air .059 econ There are other numbers

One thing to know about the tin top solid-fuel BBD, it is not an aftermarket high-performance carb. It is an emissions carburetor, lean idle circuit sometimes too lean. The original Idle Jet tube was 0.0295 very small and easy to clog. Sometimes 0.75mm drill 0.0295 will clean them out. And they will idle again but not always.

Gold mine, no, a plutonium mine of good info here.

Right at the end of that tube where the red arrow is pointing is the low speed jet. Sometimes 0.0299 drill or 0.0307 works. These little drill bits are not very common and sometimes are not a complete answer. So sometimes out of frustration One Step bigger 0.0312 1/32 drill which always works , and does not clog up so easily. And is a pretty close match to what they used back in 1967 0.0315

Now the 1/32 drill bit should be easy to get and available locally. Do not Go any bigger too rich. Now we're not doing something as drastic as it sounds, back in 67 air bleed of .059 smaller than the modern day slant six of .063 . Bigger air bleed means leaner idle circuit. With today's fuel it is necessary to increase fuel flow 3%, to match the energy of the old fuel.