PreWar Workshop: Piston stuck in the block

This old Herschell-Spillman V8 engine (1916) has been in a shed for almost 50 years. It has cast iron blocks and pistons and the engine has fixed tops.

Some years ago the engine was left to a car restorer for renovation. Two pistons were stuck but one was relatively easy taken out. Then the renovation stopped as the second one withstood every attempt with all kinds of rust removal and brut force. After some years I decided to try myself or let someone else do the job, this time with acid or lye.

A friend of mine (a very experienced restorer) offered to try too loosening the piston first.

He machined a bar to fit the big end of the piston rod and bolts were welded to the bar. Those were used to put pressure and help pull out the piston. The block (and piston) was then repeatedly heated with a hot air pistol several times to make it widen and shrink. This did not help, the piston was still stuck.

All holes in the cylinder were plugged except the spark plug hole. Lye (sodium hydroxide) was then poured into the cylinder thru the spark plug hole and the minus cable of a battery charger was connected to the piston rod. A piece of iron was mounted in a plastic plug so this metal part would not shortcut. The plug was screwed into the spark plug hole and the iron connected to the plus cable. The iron bar was now in the space above the piston filled with lye. This finally did the trick! After about three days the piston started moving down. It could now be completely drawn out of the cylinder by using the welded bolts.

The block was then lowered into a bath of lay and again connected to the battery charger. After a couple of days all rust and old sticky oil was gone. The cylinders have been inspected and to our surprise all four of them are in very good condition!

The cylinders in the other block have been honed (machine grinded) and are fine. Next step is to hone the cylinders in this block. Hopefully they are as good as they look.

Text and photos by Gunnar Geijer