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-   -   How to adjust the idle vent valve (B carb)? (https://67-72chevytrucks.com/vboard/showthread.php?t=835152)

jayoldschool 06-05-2022 08:54 PM
How to adjust the idle vent valve (B carb)?
 
Yesterday, while trying to deal with my truck that was bogging/stalling, I had minimal tools, and in my panic mode, I put a few random turns on the idle vent valve. Then random the other way. I had previously rebuilt this carb, and the truck ran perfectly. I've now remembered/researched what this valve does, but can't find how to get it back into adjustment.

What's the correct procedure for setting the idle vent valve?

https://i.ibb.co/WgMhTLQ/rochester-b...vent-valve.jpg

jayoldschool 06-07-2022 01:17 PM
Re: How to adjust the idle vent valve (B carb)?
 
Nobody remembers how to adjust the idle vent?

The Rocknrod 06-07-2022 02:07 PM
Re: How to adjust the idle vent valve (B carb)?
 
Some info here - http://67-72chevytrucks.com/vboard/s...d.php?t=679308

geezer#99 06-07-2022 02:50 PM
Re: How to adjust the idle vent valve (B carb)?
 
Is it a mono jet or model b?

jayoldschool 06-07-2022 07:09 PM
Re: How to adjust the idle vent valve (B carb)?
 
B, manual choke. I must have known how to set it when I rebuilt it... but that was a few carbs ago. I'll check that link and BRB.

Ok, yes, I'd read that one already. No idle vent info in there. At this point, I will just go with "make sure it's open at idle and closed with any throttle application".

But I'm open to suggestions/experience!

Best info I can find:

Quote:
Idle Vent Valve:

Most carburetors today will use a movable atmospheric idle vent valve in place of the fixed external vent system. This movable valve will be held in an open position only during idle and park positions by carburetor linkage contacting the idle vent arm. Any tendency for fuel vapors to collect inside the float bowl will be vented to atmos*phere through this opening at idle and park positions. As car speed increases and throttle linkage is progressively opened, the actuating lever from the linkage will no longer contact the idle vent arm thereby allowing the idle vent valve to close. This action will now return the carburetor to the internal vent system thereby once again maintaining the same pressure on top of the fuel as entering the carburetor through the air cleaner.

It is important that the idle vent valve be closed during all periods of operation except at idle, otherwise excessive richness can be caused by the higher atmospheric pressure acting upon the fuel in the float bowl.
SOURCE

geezer#99 06-07-2022 08:27 PM
Re: How to adjust the idle vent valve (B carb)?
 
Found this for you.
Down a bunch of pages (page 43)you’ll find the setting info and a bit further down you’’lol find the specs.



https://www.carburetor-parts.com/ass...r-b-manual.pdf

jayoldschool 06-08-2022 11:01 AM
Re: How to adjust the idle vent valve (B carb)?
 
Great info, thank you!

3/64-1/16 from top of carb to bottom of screw at idle. Time to find my feeler gauges...

https://i.ibb.co/gSmS1gS/Rochester-B-carb-settings.png

https://i.ibb.co/Zfggf0g/Rochester-B...vent-valve.png


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