piston marking, explanation?

[dcino]

I recently pulled the pistons on a spare engine I am building and noticed serveral marrkings cast and stamoed into them. I assumed that I had a 30 over piston because cast into the side is the # 30 and an R. The top of the piston is stamped #3 and below the number 30R and below that the #05.As a double check I had the piston checked and it fell within the standard size piston specs.

The dealer advises that the OEM pistons actually come in several sizes and these #'s reflect these very minor spec differences.

ON THE OPPOSITE SIDE OF THE ROD FROM THE CYLINDER MARK IS THE #400

Do any of you have the break down of these codes? or can you explain what they mean?

thanks
Modified by dcino at 10:04 AM 11/29/2007