Removal of a seized piston ring from the piston

[african imp]

There was a post that I read on this forum that told of someone who attepted to remove a piston ring that was seized into the ring groove, the result was a broken ring.

Some years back I was gifted a 1963 Hillman Imp engine, the head gasket had gone and water had entered the bores, the water was left and the rings were seized solid.

I used Oxalic Acid to cut innto the mess, it took about two weeks but all of the rings came out and turned out to be brand new. The engine was reuilt using the same rings and was once again a good engine.

In the case of the piston I have just treated the same way, it turns out that the ring grooves were damaged but the rings are perfect!

This piston measures 2 1/4" in diameter.

[african imp]

The Oxalic Acid will turn the piston black but does no harm and can be cleaned up in a number of ways with the right machines.
In my case I used a bead blasting cabinet.

[african imp]

Those of you who want to try the Oxalic Acid route should be able to buy it at a decent paint store, the trade use it to remove dead wood off things like doors and window frames.

Use the acid powder with hot water, it then disolves, you can leave the item you want to clean for say two or three days then wash it off in clean water. The acid mix can be kept and then re used at a later time?

[Charles uk]

Before anyone does this, it might pay to search on the web "how piston rings work" & "bead blasting aluminium engine bits" or similar expressions to understand why this web site does not recommend bead blasting power head internals.

[croweater]

That piston in the top photo is shot best place for it is the bin. I have had no issues with bead basted pistons have been using them for decades but I do the blasting. Cleaning the piston afterwards takes me longer than some guys take to build a motor.
John

[Charles uk]

Do you mask the ring grooves & gudgeon pin holes, Croweater?

[african imp]

Do you mask the ring grooves & gudgeon pin holes, Croweater?

No the entire assembly needs to be subbmerged to allow the acid to work on all surfaces.


I have found this system works and with no degrade to either the allot piston or the piston rings.


My 1963 Hillman Imp engine was the test bed, its been run for many hours now and with no issues.

[RickUK]

I struggle to see what effect the oxalic acid is having other than perhaps having a mild effect on any rust. It is a low pH acid, and will set up a dark oxide on ferrous materials - no reaction whatsoever on aluminium - but is self-limiting. It does not fizz and bubble as some might imagine with acids.
The dark oxide created is only engtsroms in depth, but would need to manually cleaned off with the help of an alkaline solution (detergent) to leave a bright surface.

Oxalic can have a mild degreasing effect which might give the illusion of cleaning parts. It is occasionally used on wood surfaces to bleach out mould and 'weathering' prior' to re-varnishing etc.

[RickUK]

I should have added that Oxalic will soften carbon deposits provided that there is not too much oil bound up in them -greatest use of oxalic around the world is in bleaching cotton fabrics.

[blokewithaboat]

Agree with Mr.croweater. That piston's shot to bits . Would that be from a 102 by any chance?

From the look of it i'd say that piston had a long time sat inside a watery wet bore. Perhaps that's why the rings seized to begin with. Seen that before with some old 102's.

A long soak in diesel for a few weeks i've found works pretty good at un-sticking seagull rings. Some gentle heat too if it's really stubborn.
Stay away from bead blasting anything on the engine's internals. That's the quickest way to wreck a perfectly serviceable part that's sensitive to how it's treated. Maybe soda blasting could be a gentler option. Not tried that yet.
Fine grade steel wool does a good job at cleaning pistons. Bit gentler than acid . But each to their own

Worst case scenario a new set of rings is cheap enough. Not sure how obtainable a new piston would be for some of the older seagulls though.

[AusAnzani]

I am with others on this, that piston should not be used in anything other than a display engine.

Alloys can become very soft if left in water for extended periods. I do not understand the technical reasons for this but have experienced it repeatedly over my outboard collecting/restoring years.

Recently i removed the barrel (cylinder) from a wartime Australian Commando outboard (number 3). In the process, the conrod literally fell apart ie main stem between the big and little end. Mind you were talking a rather thick aluminium casting of say 20 x 20mm. The piston was found to be soft also, albeit that it appears quite normal.

Point is, many of the engines we wish to restore will have had water ingress at some stage. If they dry out fairly quickly, then not a problem, there are ways to free stuck pistons and piston rings etc. But if the water sits over an extended period of time, then replacement parts may be needed.

EDIT: Adding Some pics.

1. Broken rod. I was able to break it again simply by gripping with a pair of pliers and twisting.

2. Piston removed, rings freed and given a quick clean. Aluminium is soft. Corrosion/pitting around the what was the wet area. Not reusable.

3. Cylinder after a light hone. Again, some pitting is apparent in what was the wet area so a slight bore might be in order.

Regards,
S

[croweater]

Do you mask the ring grooves & gudgeon pin holes, Croweater?

No, I know many mask the ring grooves and lands. The piston is clean before I blast them good enough to put in a motor, when we bead blast them we don't concentrate on those areas. Started doing it in the 80's in our race bike motors even new pistons, never lost a piston since so it became a habit if we were still racing guess we would trying different coatings on pistons now. Bit worried now guys will out in their yard with a hand gun blasting pistons, Seagulls are a low stressed low revving motor really all they need is a good clean piston.
John

[Charles uk]

How can you make bead blasting less aggressive to avoid damage?

By changing media?

Lowering pressure?

[croweater]

[quote="Charles uk"]How can you make bead blasting less aggressive to avoid damage? quote]

A bloke of your skill and experience asking me how to hold a gun? No worries mate got the message.

[african imp]

How can you make bead blasting less aggressive to avoid damage?

By changing media?

Lowering pressure?

There may be some slight confusion re using a Blasting Cabinet?

My own uses tiny glass beads only, you can get different grades, or use old and broken beads to give a sharper finish.

At least one forum member knows the process, as his comments indicated this.

The variables in use are many, I have put all sorts of parts into my cabinet, Hillman Imp engine blocks and suspension included.

The air pressure and distance the nozzle is from the object to be cleaned will have a very large effect on the final finish.

Using a low air pressure and fresh glass beads with do little more than polish the surface being cleaned, use a higher air pressure, say 4.00 Bar will strip most clean and dry surface junk away.