rebuilt motors=bad street cars? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

luke20 · 01-30-2002, 04:28 PM

I wouldn't think there would be any problem with driving a built motor daily, but I guess the argument is that since the pistons are forged aluminum, and the cylinders are usually ductile iron, there's two different rates of expansion, and in order to keep pistons from actually rubbing against the inside of the cylinders, large ring clearances are needed.  This causes the oil blow-by and the noise, when the engine is cold.  When the engine is warmed up, the proper ring clearances are met.  Weather there is any truth to that, I don't know.  Any opinions?

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01-30-2002, 04:28 PM	#3
luke20 Leaky Injector Join Date: Jan 2002 Posts: 68 Trader Rating: (0) Feedback Score: 0 reviews	I wouldn't think there would be any problem with driving a built motor daily, but I guess the argument is that since the pistons are forged aluminum, and the cylinders are usually ductile iron, there's two different rates of expansion, and in order to keep pistons from actually rubbing against the inside of the cylinders, large ring clearances are needed.  This causes the oil blow-by and the noise, when the engine is cold.  When the engine is warmed up, the proper ring clearances are met.  Weather there is any truth to that, I don't know.  Any opinions?