Re: {Chrysler 300} Vacuum on my 300 F
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Re: {Chrysler 300} Vacuum on my 300 F



Hi Don,

Maybe we’re saying the same thing, maybe not.  I was referring to start-up, as the car is warming up, and if the choke is too open it will be too lean.  Partially covering the air horn tells you this.   The extreme example is we got a F a few years ago where someone had not just disconnected but entirely removed the thermostatic choke adjusters and the chokes were always wide open even on startup.   But as you know those thermostatic adjusters can have a big impact on choke setting, if set incorrectly.  As for mixture screws on AFB’s I would assume as a starting point folks can gently turn the mixture screws all the way in (do not tighten with force or else you can deform the conical screw profile) then back them out 1-1/2 turns.   That’s what I do, as a starting point, let me know if I’m wrong 🙀…!

Dave


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On Sep 10, 2025, at 09:49, 'Donald Verity' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:


Sorry Dave, that is not correct. If the car runs better with a restricted air flow, it's running lean. The chokes should always be wide open when the engine is warmed up. 
Vacuum leaks can cause a low vacuum at idle, but so can the camshaft. Ram engines do not do well with high performance cams.

Don




I think someone mentioned this already but if you did the carb setup according to the FSM as Nick mentions, double check the choke settings.  
Idle the car without the air cleaners, and make sure the chokes are opening more or less the same.  If they are too far open note that too.  You can cover a carb with your hand to restrict air flow and if it runs better the choke is too open.  Usually they don’t open enough if anything.  

D&K

Sent from my iPhone

On Sep 9, 2025, at 22:13, Nick Taylor <nicksgaragesd@xxxxxxxxx> wrote:


1. What is the history of the engine? 
2. Is the throttle linkage adjusted using the factory procedure?
3. Eliminate all vacuum leaks, windshield washer harness, heater control, etc.
4. Carbs properly synched up for air flow? Use a Uni-Syn for this.


On Tue, Sep 9, 2025 at 6:18 PM 'Jay Williamson' via Chrysler 300 Club International <chrysler-300-club-international@xxxxxxxxxxxxxxxx> wrote:
Hello,

I’ve been working to make my 300 F run as bad as I possibly can and I think Ives succeeded. The car has never really had a smooth idle, so I replaced the plugs, cap, condenser, plug wires and points. Re-gapped the points to .017 and the plugs to.035. When I check the volume at idle with the car properly timed, I’m pulling 10psi off the passenger side vacuum port. That seems a bit low to me. Brake booster is holding vacuum and I have replaced all vacuum hoses. I’m running out of ideas.
Jay Williamson
Sent from my iPad

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