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Iron block vs aluminum block LS: weight and strength
Which LS engines have aluminum blocks? All car engines (LS1, LS6, LS2, LS3, LS7, LS9, LSA, LS4, L76/L77/L98) and some trucks: 5.3 L33, LM4, LH6, LC9, LH8, LH9, 6.2 L92/L9H/L94, and the hybrid 6.0s (LFA, LZ1). Iron blocks: the common truck 4.8/5.3/6.0s: LR4, LY2, L20, LM7, L59, LY5, LMG, LMF, LQ4, LQ9, LY6, L96, LC8.
Aluminum saves weight (sourced weight figures to be added), which matters for front-heavy swaps like Miatas and small imports. Iron blocks are cheaper and are the usual choice for high-boost junkyard builds.
Confidence: medium — sources disagree or are limited; check the sources below.
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Sources