internal difference 525 and 500efi
 

I was talking to a friend today and now am not all sure what the difference is. What is the difference between the 500 and 525. I know the cams, heads, exhaust and ecm. What about rods, crank, block etc etc?

I am sure some one will correct me if I am wrong, but I think in 2001, The 500EFI had Manley rods like the 525EFI. Prior to that they were standard issue forged GM rods. They are still strong, but the 2001+ are hand built vs. a crate 502 short block assembly. The heads and cam are differnt as you noted. They also went to distributorless ignition, closed cooling and long tube headers on the 525EFI . The 500EFI will be eaiser to hop up with open cooling, but the 525EFI is a much better platform in stock form. I have heard them puling in the 540hp range where the 500EFI are in the 505-510hp. Both are good motors, but the 525EFI is a great NA engine.

so rods , piston, bottom end is the same on 525 and 500?

Block, rods and crank only on the 2001 500EFI. Not sure about the pistons. I think the 500EFI has less compression.