As specified, the characteristic that the 7
critical fastener bolts of the engine have in common is precisely the “
critical nature” of the role they play.
In addition to this, each one has its own peculiar
characteristics, depending on its position in the engine and its specific task.Making
critical fastener bolts is nevertheless an undertaking that involves
custom design capability, since besides the general characteristics that these fasteners may have, every
manufacturer has its own particular requirements and precise performance to achieve, which are different case by case.
One practical example is this: there are
critical fastener bolts in both
economy cars and
racing cars, but the two vehicle categories are very different in terms of performance!
In this regard, limiting the overall
weight of the bolts in a car, including the
critical fasteners, becomes essential when an engine has to reach high levels.
This necessity leads to making choices of compromise concerning
dimensions and
strength class of the
critical fastener bolts, at times removing material from the fasteners without, however, impairing the engine’s performance.
Going into the details of the critical bolts, the
cylinder head bolts are a cornerstone of the engine, as they fasten the head to the engine block and have to respond to considerable thermal
expansions.
The
main bearing cap bolts keep the engine main bearing secure, and are not subject to the same thermal stresses, but are
tightened twice, so it is necessary to pay attention to their dimensioning.
The
con rod bolts tighten the con rod caps and are one of the critical bolts of the engine most highly stressed.
In addition to the same thermal expansions of the cylinder head bolts, they are subjected to
forces in three dimensions and are, for all practical purposes, moving components.
The
flywheel bolts, on the other hand, transmit the torque from the crankshaft to the gearbox and have to respond to important
space limitations that highly influence their design.
The
camshaft cap bolts tighten the camshaft caps and must retain their precise mechanical and
strength characteristics for the entire lifetime of the engine.
The
crankshaft bolts instead tighten the crankshaft.
They are
critical fasteners because they must always ensure perfect
synchrony between the components that they fasten.
The
camshaft sprocket and VCT bolts also must retain the exact timing between the gears or phase transformers and the crankshaft.
However, they are somewhat short elements, so they have to be treated with
micro-encapsulated bonding agents to perform perfectly.