Top Dead Center (TDC) Tool M14 x 1.25 Sparkplug

Print the centre section in 100% infill or all walls for some weight. Make sure your printer is accurately scaled (I run 100.32% to ensure accurate sizes at room temp with my PETG).

No supports needed. Print both objects upside down separately. When it's complete you may need to give it a quick rub together of the parts to ensure they move freely. It's a pretty tight fit but allows for gravity to keep it well retracted.

You can make the plunger any size for finding BDC or such too just stretch it in slicer. 

Look at my other files for the degree wheel that can attach to the harmonic balancer or crank for degreeing your camshafts.