Cylinder bores are also susceptible to thermal distortion, which is controlled by the coolant system, and to mechanical distortion of the cast iron block was reduced by extending the cylinder head bolts down through the block into what is essentially the crankshaft bearing carrier an aluminum crankshaft bearing ladder frame with integral oil pimp and oil galleries and a structural cast aluminum sump.
In this way the firing load is transmitted through the piston, conrod and bearing carrier, with the reaction taken up the bolts to the cylinder head, leaving the material around the cylinder head clamping force is also taken down into the engine, away from the cylinder areas.
The resulting accurate bore shape allows close tolerances to be used for piston and rings minimizing emission and oil consumption. This symmetrical compression was used on the Freelander 1.8 litre engine and famously, in the Spitfire aircraft’s Merlin engine.
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