No, it's not a good idea to change to 5.7 rods in a 400. IT'S THE ONLY IDEA! Or even 6.0in rods. Just to add the 5.7 rod to a 400, there is one super easy mod to do (you can do it at home). I would assume you will buy new rod bolts and have the big end resized. AFTER the new bolts are installed and BEFORE the engine is balanced, you need to grind some off the rod bolt head on the side facing the cam. Grind it at about a 45deg angle (or your machinist can do this). This provides clearance between the bolt heads and the cam lobes (this IS manditory. or 1 or more bolts WILL hit a cam lobe).
A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!