ENGINE BLOCK
Both the 3.5-liter TL engine block and that of the 3.7-liter TL SH-AWD® are constructed of lightweight die-cast aluminum. The 3.5-liter engine has thin-wall iron liners that are made in a centrifugal spin-casting process that ensures high strength and low porosity. The rough outer surface of these liners makes an effective bond with the aluminum block, enhancing block stiffness and heat transfer from the liners to the block.
The 3.7-liter TL SH-AWD® cylinder liners are made of high-silicon aluminum and are cast directly into the aluminum block. The hard piston ring sealing surface of the liners is created during manufacturing with a mechanical etching process that exposes silicon particles embedded in the sleeves. The aluminum sleeves provide better cooling thus allowing closer piston-to-cylinder clearance than iron liners afford. The alloy liners also improve heat dissipation in the area between adjacent cylinder bores, allowing the SH-AWD® engine to have larger cylinder bores, even though its bore-center dimensions (the distance between the centers of adjacent bores) is the same as the 3.5L V-6.
Both the 3.5-liter and the 3.7-liter cylinder blocks are heat-treated for strength and have deep-skirt designs with four bolts per bearing cap (providing excellent structural support for the crankshaft), thus minimizing engine noise and vibration.