I went to a mechanic and he showed me this custom piston made out of molten car pistons (there was no other option in this case). My question is: Is the scratch from the side of the piston going to affect its quality in any way? I figure that the most important part of the combustion happens above the top of the piston (and the top of the rings), so the bottom is not that important, as long as it does not scratch the cylinder.enter image description here enter image description here enter image description here enter image description here

  • Is it "made of molten car pistons" or is it a "recycled piston"?
    – Martin
    Aug 17, 2017 at 15:06
  • @Myself it's made of actual molten car pistons. Aug 17, 2017 at 15:11
  • I did not know either until today... frankly i met a lot of happy owners that have pistons like this one in their scooters. Aug 17, 2017 at 15:21
  • I cannot see the pictures here at work, but it sounds like you're describing the piston skirt in your question. If so, there is a DEFINITE risk of damaging the cylinder wall if the skirt isn't right. There is what's called "side loading" which occurs on almost every piston engine, due to how it's designed. I'd even suggest the makeup of the skirt is more important than the crown of the piston for many reasons. Be that as it may, I'll refrain from writing an answer until I can see exactly what you're talking about. Aug 17, 2017 at 15:57
  • @Pᴀᴜʟsᴛᴇʀ2 your guess is correct! Aug 17, 2017 at 16:06

1 Answer 1


I do not see anything that I would call a "scratch". A scratch would be into the piston ( below the surface ) so should not hurt an iron , steel , or even an aluminum cylinder wall. However , I see a relatively large amount of gas porosity on the surface from hydrogen gas dissolved into the liquid aluminum . This implies more gas porosity so I would be concerned about the strength of the piston . Assuming radiographic examination is not possible ; "run it and see what happens" may be the only choice.

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