I just saw a car that had a O-ringed head listed in it's mods. What is that? never heard of it. I did a search and found nothing at all. so what is it, what are the advantages and downsides. and what would it cost just for curiositys sake?

Oh yeah it was done to a TT supra motor in a lexus SC if that matters at all...

 

It uses a metal wire oring in the head around each combusion chamber. Works great when running extreme amounts of boost and cylinder pressure.