Does a turbo 400 torque converter have bigger stall than 350 turbo?

Generally, no. While there's a range of stall speeds available for both Turbo 400 and Turbo 350 torque converters, Turbo 350 converters *tend* to have higher stall speeds than comparable Turbo 400 converters.

The reason is that the Turbo 350 is a lighter-duty transmission. A higher stall speed helps compensate for its lower capacity by allowing the engine to stay in its power band longer during acceleration. The Turbo 400, being a heavier-duty unit, doesn't need as high a stall speed to achieve good acceleration. It can handle more torque and thus can achieve similar acceleration with a lower stall.

However, it's crucial to remember that this is a generalization. Both transmissions have a wide variety of aftermarket converters available with vastly different stall speeds. You could find a Turbo 400 converter with a higher stall than a Turbo 350 converter. The stall speed is determined by the converter itself, not solely by the transmission it's used with.