When Buick went from odd fire to even fire, they had to split the crank rod journals to evenly time the pistons. They had to split the rod journals 30*. This added material betwen the rods. (the odd fire cranks had shared rod journals, like a small block chevy.) This added material required the block to be redesigned with the bores staggered farther apart. (the passenger side of the block needed to be farther back and the drivers side needed to be farther forward.) BUT, that would have cost GM ALOT of money to re-tool, so they just hung the rod on the piston off center to compensate for the added material. (.098") Along with a rod that is not symetrical, they obtained the required clearance. On a >600 hp engine, this off set is not a problem.
Enter the Indy and Busch racing series, and now the off set DID become a problem, in that the rods wouldn't have an even load on the bearings, and would also bend/break the rods. So GM engineers, staggered the cylinder bores enabling the pistons to be hung directly centered over the rod journal. Better design on the late Stage II block ONLY. The early StageII and all Stage I and production blocks are off center. The on center StageII blocks are not needed, unless you plan on making over 800 hp. The on-center blocks also require different intakes and timing covers, too. (you can machine .125" off of a stock timing cover parting surface to allow it to be used on a on center block.)
Thank you for that VERY complete answer! I didn't realize there was so much done in the evolution of the 3.8. Heh, now I have some good bench racin' material to throw at my buddies!
