Big End Oil Groove

[Hedd_Jones]

Just to give you some perspective from other forms of engine. Not only do steam engines close the exhaust before the piston reaches the end. They also open the admission. This cushions the piston at the end if its stroke. Remember most are double acting.

You can mess with the valve. Reducing the exhaust lap, or reducing the 'lead'. This gives a free er running engine. More revy. But doing so means your more likely to have little end trouble.

Mine has too much exhaust lap.