Hey dudes jimmy here , MR D thanks for the last info, good stuff. My new story is at 3000 RPM i set my timing at 30 right now i can unscrew idle screw out past contact and it wont idle down to get it to work i have to retard the spark to full advance at 22 . And my MPG goes to about 13. AND LASTLY my bbd main jet # is 120 where can i get the 2 steps higher jets curently i have to screw the mixture scwers out 5 full turns out to get it to run smooth vacuum is 22

Why were you trying to set the timing this way instead of the correct way (at idle)?
That probably means you've got internal carburetor problems -- a sloppy throttle shaft, for example, and/or throttle plates not correctly installed on the throttle shaft. What do you know about the history of this carburetor?
All Carter jets start with the number 120. The three digits after the 120 are the jet number.
You already said your mileage is poor...you want to add more gas? Why? What makes you think your running issues are jet-related?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

well dan on the timing issue all the articals i read say to go for total advance thats whats important right,
and the carb issue was the bottom of the carb was warprd to much for the gasket i blocked sanded it flat, now it is smoother but still idles to fast at 30 total lastly jet size if i upsize my jet taller i should be able to screw my mix screws in to about 1/2 or 2 turns out maybe the rest of the carb will follow so the flow transisions properly

By the way what is the standard jet size for carter BBD on slant six

Total advance is important to the car's highway performance and fuel economy, mostly; the total-advance figures you read about are for use in reworking the distributor, NOT for setting base timing!
No. Main jet size does not affect idle mixture.

Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.