Lycoming SB388C Part 3 Alternate "Locally Manufactured" Tool
Description
CAD version of the tool called out in Part 3 of Lycoming Service Bulletin 388, Revision C, "Procedure to Determine Exhaust Valve and Guide Condition". The full text of the service bulletin can be found here: https://www.lycoming.com/sites/default/files/Procedure%20to%20Determine%20Exhaust%20Value%20and%20Guide%20Condition.pdf This example has been made with the 5/8" rocker shaft boss directly, instead of the 7/8 boss for you to press a rocker shaft bushing into. It has also been made for a dial indicator with a 3/8" shank. I've included the FreeCad .FCStd file and a .STEP file so that you can edit these parameters in either FreeCAD or the CAD program of your choice. Being cheap as ****, I'm trying this as a 3D Print in PLA. I'll update this summary to let the community know if that works or not. **Update 14 Jan 2020** After using this in the Real World, I can confirm what most mechanics already know. That is that engineers have no idea what they're talking about, and have never actually tried fitting tab A into slot B in real life. I've adjusted the thickness of the tool overall, the depth of the pocket on the front, moved the position of the two side set screw holes to bite further out, and changed the shape of the pocket on the front to actually fit on larger angle valve engines. I've also added a bit of a fillet to the back edge to provide a little more clearance. Lastly, I counter-bored the body portion of the dial indicator clamping screw hole a bit larger. I tried making the stem extensions as shown in the SB per their plans, but that's not a part that lends itself to printing in PLA. I would recommend that you build that part from aluminum tube or machine it from bar stock. Thankfully I have a young apprentice that was able to crank this part out on a lathe with ease with zero notice. (Shout out to ma boy Sean!)
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