What difference does the length of the connecting rod make? I am acquiring a parts list for my 460 but am stuck at connecting rods and I am not sure what length to go with 6.605", 6.7", or 6.8". What difference does each make?
Do you have the other specs like deck height, compression height, crank stroke, etc?
If you go to Ford Racing's web site and download their parts catalog, toward the end there's a great diagram of how to calculate compression ratio. Even though it's geared toward calculating that, I think it's the best way of understanding what a different rod length would do.
The short answer is that it will dictate where the piston crown will be at TDC. If the rod is too long, the piston will go too far up, and you'll smack the cylinder head. Too far down, and you'll lose compression.