LO 8-4 Explain the purpose and methods used to increase the rigidity and strength of a diesel engine cylinder block

1.2. Cross-Bolted Blocks

Cross-Bolted Blocks

A variation of the deep-skirt block is a cross-bolted block. Also known as tie-bolted or bolster-bolted blocks , this design uses additional, horizontally placed bolts to connect crankcase walls of the block to the main bearing caps. Cross-bolted blocks permit the use of more than the traditional two or four vertical bolts to hold the main bearing caps Figure 28. By tying together the block walls and main bearing caps, cross-bolting limits crankshaft flexing, stiffens the engine’s structure, and reduces overall vibration Figure 29. This type of block reinforcement technique permits further weight reductions than deep-skirted blocks because the crankcase walls do not extend far past the main bearing caps.

FIGURE 08-28: A cross-bolted main bearing cap in an aluminum block with cast iron liners. Cross-bolting is used to enhance engine block strength and rigidity while reducing noise and lowering engine weight.

FIGURE 08-29: This older Mack E7 block is cross-bolted to stiffen the main bearing bore.