The stud girdle puts the lower block structure to use in much the same manner as a cross-bolt, tying all five main caps together and then anchoring the assembly to the pan rail. We tend to think of the forces on the cap as being straight down, as in the direction of the main-cap fasteners, but, in fact, the forces acting on the cap come in three axes. A high-strength main fastener will provide a substantial amount of clamping force in the vertical axis, but in the stock configuration, there is little control in fore-and-aft and side-to-side restraint. In fact, the cap motion through rocking forward and back as the crank and block flexes under load, and side-to-side as the connecting rod transfer forces to the crankpin contribute much more to cap walk than is commonly recognized. The girdle is fixed to the far end of the cap, a position that provides the maximum mechanical advantage in terms of stabilizing the cap. It provides very little reinforcement in the vertical axis, but dramatically increases the stability in the other two axes, and therein lies the real benefit. A cross-bolted main cap structurally works in a similar way.
Since its introduction, the CRE main girdle has been used in some pretty high-powered applications, and reports are that cap walk problems have been significantly reduced. An extreme example is Jerry Timmerman's rail, with a B-1-equipped production wedge developing 935 hp and running the stock two-bolt factory main caps and the CRE girdle. After a season of racing, block inspection revealed no undue duress, while the previous season was marked by two bottom-end engine failures. That's not to be taken as definitive evidence that the main girdle is the ticket to building a reliable 1,000hp production wedge, but we'll take it as evidence that it will impart an extra measure of security in our 600-plus-horsepower street engine.
What's Cap Walk?
When a main cap is torqued to the block, it's contact area at the block is less than a square inch of metal on metal, and the hope is that these two surfaces are clamped tight and locked together. In a low-stressed application, the fastener does that, and the assembly is locked down solidly. In a high-stressed environment, it's a different story. Caps distort, and, in a worst-case scenario, actually move and deflect noticeably. Evidence of this can be seen as metal transfer and galling at the mating surface of the cap and block. It's not hard to recognize cap walk by inspecting these surfaces, but what can prove difficult is minimizing the condition. Adding stability to the main caps is the goal, and to accomplish this, the motion of the caps has to be minimized.
There are a variety of stresses on a cap, acting upon it in all three axes. Fortunately, there are steps that can be taken to combat the effects of these stresses. Adding clamping load is the first step, and this can be accomplished with premium fasteners. Higher quality main caps can also be a benefit here, helping to reduce the distortion of the cap itself. The deeply skirted big-block Mopar can be used to an advantage by tying the main caps to a structure that is just absent in most competitive engine designs. The CRE main girdle gives the enthusiast a simple way to accomplish this. If you're building a high-powered wedge based on a stock block, the girdle system may be your best weapon in the battle against cap walk.
 Large, hardened washers and...  Large, hardened washers and a second set of nuts tightened on the studs retain the girdle to the main caps. Only snug the fasteners lightly for now, and recheck the alignment to the counterweights. If everything looks good, torque the nuts to the recommended 70 lb-ft of torque, with Locktite on the threads. |  After reinstalling the oil...  After reinstalling the oil pump pick-up tube, we mocked-up the oil pan using a lump of clay to check the pick-up tube depth within the pan. The extra quarter-inch of girdle thickness makes the pan sit a little deeper. This is not usually a problem. we just tweaked the installed pick-up slightly, and had about 0.200-inch distance to the bottom of the pan. |  The CRE girdle works perfectly...  The CRE girdle works perfectly with the stock windage tray, and actually gives it a nice uninterrupted surface to seal to. |
 Buttoning things up, we installed...  Buttoning things up, we installed the factory high-capacity pan, and torqued the pan nuts to the recommended 15 lb-ft of torque. The installation ties all of the main caps together, and ties the assembly to the block's deeply skirted rails. |  The girdle adds a quarter-inch...  The girdle adds a quarter-inch of thickness, which drops the pan by the same amount. This should not represent any clearance issues in a stock chassis. | |