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Labor Day Putting down your wrenches or time for
MORE wrenching? 
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Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
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| | | | Joined: Apr 2009 Posts: 54 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2009 Posts: 54 | Cleaning out my carter YF carb.Anybody know how the Low speed jet is set.No mention on any manuel ive seen? | | | | | Joined: Feb 2008 Posts: 130 Wrench Fetcher | | Wrench Fetcher Joined: Feb 2008 Posts: 130 | I am thinking it is set and not adjustable, but not sure. You aren't taling about idle speed or idle mixture are you? | | | | | Joined: Feb 2004 Posts: 29,740 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,740 | "Low-speed jet"- - - - -are you thinking about the idle mixture jet, the one that screws into the carburetor body just above the throttle plates? If so, start by gently closing the needle valve all the way clockwise and turn it back counterclockwise about 1 1/2 to 2 turns. This should allow the engine to idle until it warms up sufficiently for a final adjustment. Attach a vacuum gauge to a full manifold vacuum source like the windshield wiper hose port. With the engine idling at around 400-600 RPM, turn the idle jet clockwise until the vacuum starts to drop, and then back it out until the vaccum maxes out. It might be necessary to slow the idle speed down to get the best compromise between idle speed and steady vacuum. A good idle vacuum reading will be 17 to 19 inches of mercury, depending on your camshaft, ignition timing adjustment, and general health of the engine.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Apr 2009 Posts: 54 Wrench Fetcher | | Wrench Fetcher Joined: Apr 2009 Posts: 54 | Yes it's the low speed jet and I think it's set,but thanks for the info on the idle mixture. | | | | | Joined: Aug 2000 Posts: 248 'Bolter | | 'Bolter Joined: Aug 2000 Posts: 248 | Always something to learn.....
Jerry... your explanation about the vacuum hookup on a Chev engine.... NOW I know why I was getting erratic vacuum reading.... Dumb A** I connected my vacuum gauge to a tee fitting on the vacuum line for the dizzy and been getting readings from ABOVE the throttle plate...... can hardly wait to get back to the barn this week end to correct my mistake.
It's amazing what you can learn from this forum just by reading other postings.
Kudo Jerry.
Bob C.
Bob C.
CMP Heaven
The Hammond Barn
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