EAM 6518A) is exactly the engine valve key you are looking for. Officially, it is classified as an Exhaust Valve Keeper (or valve spring retainer lock / collet).

Key Details:

• Fitment: This is a widely used valvetrain component for vintage Ford and New Holland 4-cylinder gas tractors equipped with 134, 172, and 192 cubic inch engines (typically spanning 1939 to 1964).

• Common Models: It fits the Ford 9N, 2N, 8N, Jubilee, NAA, the entire "Hundred Series" (500, 600, 700, 800, 900), as well as the early 2000 and 4000 series 4-cylinder tractors.

• Hardware Specs: These are used specifically with rotating exhaust valves. You need two keeper halves per valve to lock the spring retainer to the valve stem.