I have just had my Block bored and pistons replaced...the friend i have is a diesel mechanic and is helping me with this build but he's curious about which piston is supposed to be top center because he's used to it being number one which in his work has always been on the front of the engine..when we place the timing gears on using the manual its the rear cyclinder thats up...he's just being sure before we go further...thank you for the help. Its a two cylinder Diesel btw.