Piston – Single Valve Poppet Engine

This is the initial process of machining the piston for my single cylinder poppet valve engine.

This piston is being machined out of cast iron, I can hear the screams of how heavy this will be and the resultant vibration when the engine is running. However, a cast iron piston and liner is one of the best pairs of material to machine and run.

offering up the cylinder to check the fit

When machining to size I take it steady, small cuts, lots of measurements and start offering up the cylinder to the piston as a rough check. This assumes you make the cylinder liner before the piston, I think this is the easiest way and always do it this way round.

offering up the cylinder the wrong way round

Offering up the piston the wrong way is not a serious check, but again slows me down and gets me doing lots of measurements.

Before removing the piston I drill into the bottom end and machine as much as I can in the lathe.

Drilling to the full depth of the slot is useful as it gives some clearance for the slot drill to operate in the next operation.

All now turned, milled and drilled for the gudgeon pin.

final piston

The final cast iron piston weighs 14.9g and is 17.2mm in diameter and has a height of 16mm.

Leave a comment