Subaru EJ253 Coolant Port Resurfacing Tool

WARNING: Improper use of this tool can result in damage to your engine block. Don't use it if you don't fully understand what you're doing!

NOTE: when printing, increase Infill to 25% – all other default settings should be fine.

Affix pieces of 800 or 1000 grit wet/dry sandpaper to each of the cutting faces using spray adhesive (3M/Scotch ‘Super 77’ or equivalent). Once dry, trim the excess along the inner and outer diameter of the tool so it resembles what's shown below. 

Note the condition of the port's sealing surface before you begin as this will help you determine when enough material has been removed.

Mix about 1 cup (8 oz/250 ml) of water with a few drops of dish soap/washing up liquid to use as a cutting fluid. Adding a few drops to the sealing surface will ensure that the sandpaper stays clean, and also help to keep the tool from binding during use.

Using gentle, even pressure, rotate the tool in a single direction for 10 to 15 revolutions. NOTE: be sure to replace the cutting fluid between each run (paper towels work great for removing the old, dirty fluid!).

As you progress, you should notice the surface finish of the port improve, as can be seen below. Keep in mind, this process will take some time – so be patient, and don't rush things! NOTE: 30-45 minutes to resurface one port is not unreasonable.

Resurfacing is complete as soon as the surface finish across the entire port becomes uniform in its appearance (unlike the port in the image below, which was only about 90% complete – but you get the idea 😉).