[Bob Carriere]

The piston rings are probably rust welded to the cylinder walls....... amazingly strong when you consider the surface area of the ring against the cylinder wall.

I have had better luck with some mechanical force than with diesel, ATF, rust blaster, Gibbs, etc.....

Cut yourself a good sturdy piece of wood that will almost cover the whole face of the piston...... leave the diesel fuel 1/8 of an inch..... you have the bottom end open...... locate number four and hopefully it is probably half way up or down...... alternatively tap the piston from the top and tap the crank ( using a block of wood ) from below...... be patient.... it will eventually break free....... you may need to polish the cylinder wall with 600 grit emery paper soaked in fuel...... rings may need to be replaced....... has worked for me every time on old Allis Chalmers tractors that were left in the rain. Having someone to tap from the top as you tap from underneath is a God send..... don't ask your helper to do the tapping from below...... the oil drips will spoil the friendship. I have done this with the engine still in the tractor frame.....and my old WC and C are still running.

cheers