Originally Posted by demonkevy666
AAC (aluminum aluminum chrome) engine pinch so tight when over heated the stretch the piston. The when they cool they're about 0.005 thinner and slightly above TDC.
Nice info but far from real. It is all depending on the used materials of the piston and sleeve. The piston has a high level of silicon (up to 30%) for more strength and less expansion. The sleeve has a larger expansion rate so in cold conditins you do have some pinch which also helps a cold start. Because the sleeve gets more cooling than the piston there will be a ideal fit on operating temperature.
If you choose a piston with a higher expansion rate then in cold conditions the piston will not build up compression but on temperature it will have the ideal fit, this is not what you want.
The ideal situation is to use materials with no expansion, after running in it will have the perfect fit on every temperature and no heating up or perfect operating temperature is needed.
But that is not possible.... although sometimes you get a perfect engine with no cold pinch which is easy to start and can be brought to operating temperature in a faster time.