Lionel Heavyweight Coupler Help

I went out and looked at my left over couplers. I converted all passenger cars to KDs. You can remove the truck and adjust the coupler spring. I never did that on mine and they would nearly all uncouple sporadically. Kadees solved that. You might be able to insert a tooth pick end into the spring to tighten it up.

You can see the coil spring on the uncoupler bar, just above the red oval in your picture.

The truck can be disassembled, that spring can then be stretched to increase its tension. That should solve the unwanted uncoupling.

You can also adjust the angle of the magnetic uncoupling tab, where it touches the uncoupling bar.

Or, you can just glue the coupler shut.