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OK, so here’s the story.
37 Packard 115 C.
Stock carburetor.
I have a constant issue with the air fuel idle mixture screw drifting. This causes over fuel condition, rough running, etc.
In the picture was my fix.
Does anyone have other suggestions on how to keep the needle valve screw from adjusting out.
This usually happens after I’ve driven the car and parked it and let it cool down.
The car started right up at the garage. Ran great until I got about 2 miles from our dinner stop..
When I parked I turned the screw about an eighth of a turn, maybe like a 16th into the lean and the car idle right out.
It ran ok back to the house and then t turned about 1/8 turn lean and it smoothed out , better than the parking lot adjustment.
Thanks

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Wonder if a couple of external tooth star or serrated lockwashers would provide enough grab to keep vibration under control. One at the carb between spring and base and the other at the screw head might bite into the spring and each surface to hold it in position. If that would not work perhaps a small dab of gas resistant glyptal or varnish at the threads would seep in just enough to lock it down but would still "crack" open to allow future adjustment.

What carb are you using,a Stromberg? The way you have the safety wire will tend to open or richen if there is any flexing of the vacuum line,that it is tied to. The original factory carb was CHandler-Groves or later known as Holley.The original factory replacement was WA1 Carter. Even though the C-G carb was said to be bad,I have known two 115C owners who used the C-G carb with no problems.

A touch of low strength locktite should solve that.

That's an odd situation. Are you sure that you don't have a leak at one of the carburetor body gaskets or perhaps a manifold gasket?
I believe that carburetor should have a thick heat insulator/spacer between it and the manifold. It doesn't appear to have one. Lack of the spacer can allow the carburetor to get too hot, which can affect the fuel mixture, especially at idle and low speeds.
If the idle mixture screw is actually turning, putting a small washer or two or three under the spring should stop it. It may be the wrong spring for the application.

Thanks to all
I see the flex opening the screw, missed that one 😊
Stromberg BXOV 2 I think ? ( or 3)
This is what was installed by last owner,
I have the original GC that needs rebuilt.
This evening I installed a rubber grommet and a small O ring in place of the spring.
I like the idea of a star washer, see how the rubber works,

Been a while since I checked in.

We took a trip to Austraila, New Zeland, and Fiji in Sep. Oct. so I have not driven the car much.

I did replace the spring with a panel grommet that was about the same heigth as the spring in mid August.

I was busy finishing up projects around here so I did not drive the 37 much.

Now that I am back I have had a couple of chances between the rain storms to drive into town.

I'm glad to report that the carburator is staying in adjustment.

I got in to back it out of the garage late last week , set the choke with 1 full depression of the pedal and hit the button, the engine started to roll and before 1 full revolution it fired right up and came to a good fast idel with very little black spitting from the tailpipe.

I think the gromet also helped seal up the idel screw threads improving the air fuel ratio .