Re: {Chrysler 300} Vacuum on my 300 F

Ryan wrote "but have seen this on more than one occasion with B/RB’s, valley pan gasket failure at the runners.

When I got my F I had a bad valley pan leak and gasket failure at the runners. Good idea to check!

Otherwise its a classic vacuum leak that needs the classic vacuum leak checks, throttle blades, carb gaskets, intake gaskets and the carbs themselves. An unlit propane bottle used around every suspect can be helpful.

-----Original Message-----
From: "Ryan Hill" <ryan_hillc300@xxxxxxxxxxx>
Sent: Tuesday, September 9, 2025 10:58pm
To: "Nick Taylor" <nicksgaragesd@xxxxxxxxx>
Cc: "Jay Williamson" <letterpressman@xxxxxxxxxx>, "Club International Chrysler" <chrysler-300-club-international@xxxxxxxxxxxxxxxx>
Subject: Re: {Chrysler 300} Vacuum on my 300 F

Have you done a compression test…..are all cylinders more or less equal?

Have you checked the distributor for play? If it’s worn you will never keep the dwell where you need it.

Are the carbs in good condition internally? Blocked or partially blocked passages, incorrect float levels, bent or worn throttle shafts??

The vacuum is low at 10. Other things to consider in terms of poor vacuum and rough idle; if there are no obvious leaks externally there’s a chance it could be leaking internally into the lifter valley. I’ve never worked with cross rams but have seen this on more than one occasion with B/RB’s, valley pan gasket failure at the runners.

Good luck with it.

Ryan Hill

On Sep 9, 2025, at 7:13 PM, 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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