Nova_Dust

Been reading some tech here and there. Increase the stock bore from, say, 75mm to 75.5, 76, 77, and what not. Then they talk about using stock oversize/overbored pistons.

So my question is, is the actual piston bigger in diameter or what makes the piston bigger? Bigger piston rings to fill up the gaps of a bored cynliner?

Thanks

imported_trackhack

The outer diameter(OD) of the piston must reflect the inner diameter(ID) of the bore size, minus some clearance.

Oversized pistions must be installed with rings manufactured for that specific pistion size and as always your ring endgaps have to be set.

Piston to bore clearance specifications differ from engine to engine but correct me if I'm wrong it is usually around .001"-.002"

There are experts on this board that will give a better answer than I, but I believe I'm in the ballpark with this one.

imported_GoldBadge

So basically, an oversize piston requires an oversize bore...right?

bbarbulo

iTrader: (2)

honda offers one stock oversize piston for rebuilds. the actual piston is larger than the stock bore, so the cylinder block needs to be machined (bored out) and then honed to accept the new larger ristons and rings.
this machining is critical if it's not done by a pro like Steve_Leitner then the cylinder walls may end up tapering, or not being parallel, or the bore centers being off center, or not being square to the crank journals, etc, etc...

Nova_Dust

So the actual piston is larger, I see. Thanks