I'm in the process of assembling my newly rebuilt M52 out of my 1998 328is. The goal of this project was a completely stock rebuild.

I've been able to reuse all of my bottom end components with the exception of the pistons that I ordered from Top End Performance, a JE reseller. These parts were ordered to be identical to the factory parts with the exception that they fit a slightly larger 84.5mm bore (84.0mm is standard). The only noticeable differences I've been able to discern is that the exhaust valve reliefs are larger than stock, but the intake reliefs appear to be the same as stock.

I read somewhere on these forums that the geometry of the M52 results in the piston faces being 1.8mm below the deck. I'm not sure how the person arrived at that number and I don't think BMW publishes it anywhere. So I naturally grew concerned when I installed my pistons with the stock rods, measured the depth with a digital caliper and found the faces of the piston below the deck by "only" 1.1-1.2mm.

I called TEP and the owner assured me that:


  • The 1.8mm number is bogus
  • They have used these pistons in many M52 stock rebuilds with no issues
  • That 1.1-1.2mm is exactly what I should be seeing for a stock application (stock pin height, rod length, and compression ratio)


While I realize that the piston I'm using is, for all intents and purposes, a custom part (though it is designed and marketed as a stock replacement), I figured I'd ask you guys if the 1.1-1.2mm number is correct for a factory / stock application. In other words, if I measured a factory new engine, would the faces of the pistons be below the deck by 1.1-1.2mm?

Thanks for any insight.