Project MR6
Pistons
Pistons are probably the highest stressed items on a high-boost powerplant. Hypereutectic pressure-cast pistons are fine for low-to-moderate boost applications, but for serious boost, forgings are the way to go. Correct piston-to-cylinder clearance is critical, and the block should be bored or honed only when the machinist has the new forged pistons in hand. The stock 1MZ rods are a bit scary, and we'd already sent a new Toyota rod to Crower to have custom forgings built. Rpm is vastly harder on rods and rod fasteners than extra boost and combustion pressure, but cast or powder rods can suffer compression fracture in severe enough applications. Our engine had one bad rod cap and damaged bearing, though the crankshaft hadn't been damaged beyond polishing repair.
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