As part of our upcoming Mopar 440 stroker build, we felt it necessary to upgrade to billet steel main caps. Luckily Milodon was just coming out with it's newly redesigned steel caps manufactured to accommodate the installation of "Hemi-style" side cross-bolts. According to Milodon President Steve Morrison, the caps are available for both the 383/400 B blocks and the 440 RB blocks and they incorporate an improved steel alloy for additional strength. Morrison also explains that unlike most caps these are configured to accept larger 3/8-inch cross-bolts instead of the more typical 5/16-inch bolts. They take a bigger bite of the cap material and form a very rigid structure around the crank.
We had a choice between stock mild steel, ductile iron and aluminum; the characteristics of each which are widely debated among racers, engine builders and manufacturers. We chose Milodon's billet steel caps for maximum reliability. The cross-bolting feature is attractive and Milodon's machining procedure for the main web braces offered a good approach to maintaining strength. Cross-bolting is a considerable plus in the effort to prevent main cap walking, a problem often noted when upgrading or rebuilding performance applications. Main cap walk is caused by the crankshaft being forced downward, overloading the factory main caps and fasteners, altering main bearing oil clearances, and allowing the crank to wiggle and flex to the point of bearing failure. Not all shops are equipped to handle the machining requirements so we chose one of the best around, QMP Racing Engines in Chatsworth, California.