Many people might consider
this sort of clearance to be excessive, but here's why they might be wrong. If you have ever removed a head from an engine and rocked the piston back to forth in the bores, you may have been surprised at how much it moves.
While your first thought may have been that this might seem wrong, it's likely that you've got nothing to worry about. To understand why there's so much clearance, we need to understand how the piston expands when the engine's running.
The crown of the piston is exposed to a lot more heat than the skirt, and hence it expands more. When the piston is manufactured, the sides aren't actually machined parallel. There's a slight barrel shape to the skirt,and the skirt is wider near the bottom than it is at the top. When the cylinder are bored and honed, the clearance between the piston skirt and the cylinder wall is set at a point that's typically nearer to the base of the skirt, where it's wider than the crown.