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9. The forces that the reciprocating assembly can exert on the block can sometimes overwhelm the main bearing caps and the fasteners that hold them in place. Under heavy loads, the caps can shift or “walk” from side to side. This movement can then cause the threads of the fasteners to become fatigued. Eventually, the main web cracks, leading to a loss in oil pressure and possibly catastrophic damage to the block and rotating assembly. While aftermarket blocks often utilize splayed four-bolt main caps to combat this, not everyone has the budget to buy one. Main cap girdles, such as the D.S.S. Main Support System pictured here, are a cost-effective way to add strength to a production block. While some girdles are made from steel, the D.S.S. piece is made from billet 6061-T6 aluminum to effectively dampen damaging harmonics, which the company says virtually eliminates main bearing walk.