The Stovebolt Site Forums The Shop Area Engine Shop Chevy 409 Questions

Single most common mistake w/r/t displacement: remembering part of what you did, but not the piston oversize.
409 stroke: 3.50"
427 Z11 stroke: 3.65"
427 Mk II stroke: 3.76"
454 stroke: 4.00"
348 bore: 4.125"
409 bore: 4.3125"
427/454 bore: 4.251"

409 bore + 427 Mk II crank = 439"
409 bore + .045" + 427 Mk II crank = 447"
409 bore + .060" + 454 crank = 481"