RE: {Chrysler 300} slight surge at minimum throttle between 40 and 60 MP

I did Bob, no change…I am running the Chrysler orange box on this car...not the dual point.

From: Bob Merritt <bob@xxxxxxxxxxxxx>
Sent: Tuesday, April 22, 2025 07:36
To: James Douglas <jdd@xxxxxxxxxx>
Subject: Re: {Chrysler 300} slight surge at minimum throttle between 40 and 60 MPH

Hey Dr West Coast,

I wonder if it might be the vacuum advance hunting.

Have you tried running that speed with the vac advance hose disconnected

and plugged? Quick and easy to do.

Bob

On 4/22/2025 10:00 AM, 'James Douglas' via Chrysler 300 Club International wrote:

I have been trying to figure out why I have a slight surge at minimum throttle between 40 and 60 MPH for six months. I have looked at everything. I cannot find it.

I have tested and checked everything on the fuel and ignition. The thing I do not own is a A/F meter that I could stick into the bug in my exhaust and look at what the A/F ratio is doing while I drive down the road.

At lunch last week a bunch of us discussed this problem, it is very subtle, and one person suggested that it may be the combination of the gearing and the three step metering rods.

I did put in a set of 2.76 gears in the car. Is it possible that the engine RPM with the 2.76 gears is tossing off the vacuum curve such that the pistons in the AFB are not moving the step-up rods in such a way that I am getting a lean mixture at minimum throttle between 40 and 60 MPH?

The rods and jets were likely picked at the factory to match the cam and the airflow of this engine. Perhaps the move from a 3.23 rearend to a 2.76 has tossed that calibration too far off and the combination is leading to a lean condition at those RPM’s under a very light load and below the secondaries coming in?

Thoughts? James

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RE: {Chrysler 300} slight surge at minimum throttle between 40 and 60 MPH