Giving 617 pistons a new life

[rorax]

Hi all, I'm curious what others have done to combat worn out ring grooves in turbo 617s etc where the Pistons are expensive and a PITA to find.

My pistons are all worn the same on my engine. .008 axial play on the top land, .004 on the mid and .002 on the oil ring. While 2 is acceptable, the other grooves are just too far gone. I've found that there are 2 options to fix this without buying a new piston, and both involve a lathe.

Option 1 is to get shimstock spacers which are just a few dollars a piece, standard sizes are .016 and .030. so just add the thickness of the shim and the ring, add a thou and a half to that for clearance and cut the groove to that size. Bingo.
The only worry I have is how this affects ring seating during the break in period. Probably not a worry really because they're put on top of the ring, while 90% of the impulse is being transmitted through the bottom of the land. However these small considerations are necessary when you want them to outlive yourself.

Option 2 is to have custom rings made that are x units taller. The main problem is that there are only so many available sizes, so you can't just add a 'couple' thou to the height, more likely to add something like 30 at least at a time, if you're lucky. What I don't like about this is the increase in frictive surface, which is a huge factor in cylinder life.

When I add the future hauling of ass many times around the earth into the equation, I just feel like I want to get these things right. Don't take anything I say as verbatim, half of this is talking out my ass 😁

Feel free to bash my logic where necessary