Engine disassembly – stuck pistons

OK, I’m on my 5th flathead disassembly and I’m getting better at it. Some come apart better than others and the one I’m working on now has some seriously stuck pistons. I de-rust the block for a few days using an electrolysis process, which works great, but these pistons are in tight.

The first flatty I took apart I juts pounded the crap out of them pistons to remove them, but I’m trying not to be as hard handed as I was with the first. One question I have is if anyone has used Sodium Hydroxide (Lye) to dissolve aluminum pistons. It’s a strong base chemical (opposite of acid) and, from what I’ve read, will dissolve aluminum but not affect cast iron.

I was also going to make a tip for my pneumatic hammer that I will try to at least break them loose a bit. Hopefully enough that some penetrating oil can find its way in between the cylinder wall and piston.

Any other ideas and techniques you use would be greatly appreciated.

Thanks,

Sid

If your trying to destroy aluminum, I've heard mercury would be the way to go. Check this out: http://www.popsci.com/scitech/article/2004-09/amazing-rusting-aluminum

If you can find some mercury and make it into a paste.....

Muradic acid works, but I don't know about dissolving whole pistons. It is really good for if you have small chunks of aluminum galled to steel, ie...melted piston pieces stuck to a cylinder wall or underside of a iron head. Should be able to find it @ most hardware stores. Just soak a rag with it and leave it on for several minutes. Does not seem to affect iron or steel at all.

I've heard of the old timers heating seized bolts and then appying candle wax letting it melt into any seam it can find. After it cools they claim the bolts would turn right out. I never tried it, so I don't know for sure.

Stuck Flattie

Hey Sid

Just for info purposes, Marvel Mystery Oil is a great carbon disolver. Maybe pour some on top of pistons and let it seep around them? Maybe a lot of carbon keeping them stuck. Maybe not.........just a suggestion.

Shakey

I'm assuming you already tried pouring liquid wrench in the cylinders and let it sit for a few days... Would it help if you applied heat and then let them cool... Are they seized together because of the reaction between unprotected aluminum to cast iron contact...

Sniper said:

I've heard of the old timers heating seized bolts and then appying candle wax letting it melt into any seam it can find. After it cools they claim the bolts would turn right out. I never tried it, so I don't know for sure.

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That works, but you don't heat the bolt, you heat the surrounding metal to make it expand and allow the wax to wick into the gap.

A 50/50 mix of acetone and power steering fluid is a great penetrating oil.
I have also heard the wax trick works but I never tried that one.
I have used lye on snowmobile engines that melted pistons and left aluminum on the cylinder walls. I actually used Drain-o. Be carefull with the stuff, if it corodes aluminum just think what it'll do to your skin!

So far this week I've tried:

Off the shelf (expensive) penetrating oil... no luck
I tried using Sodium Hydroxide (Lye) then penetrating oil... no luck
I had a hair brain idea and filled the pistons with dry ice to shrink... no luck

Next steps are:

1. Use acid for a bit then apply the 50/50 acetone/power steering fluid.
2. Plan B... or does that make it Plan E. Drill the tops of the pistons out and split them down the side... I really hate having sharp tools inside the cylinders.

Sid

If you drill out the tops of the pistons, you will only get as far as the wrist pins, so the connecting rods will still be attached...

I know of a fella that always used Diesel Fuel for stuck pistons. He swore it works every time. The gentleman says you have to let it soak a day or two, but he swears it works. I have never tried it, but I have heard this from more than one person as well. Might be worth a shot!

Just a safety thought - be careful of dumping too many chemicals in there. Get the wrong combo and you could get an explosive chemical reaction or at least some seriously bad fumes. Lye is a VERY strong base and doesn't play well with acids.

Well, I finally got the pistons out.... the hard way. I ended up breaking out the top of the pistons. Then I chisled around the wrist pins until I could get a chisel on them and not be banging on the rod. One good smack on either side of the wrist pin split the piston right below the lower oil ring where it was the thinest. I was able to knock the piston out easily. With the top of the piston still in, I could then split it with the chisel and it dropped out the bottom. It took about 2 hours and I only managed to smack my hand twice with the hammer.

After all that work, it failed magnafluxing.

Back to craigslist to find another engine.

Sid

would liquid wrench eat rust then pour diesal in it then try to break loose[P

Sid said:

After all that work, it failed magnafluxing.


Sid

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DOH! That bites.

Ya, it does. So far it seems like I've purchases every cracked flathead block in Oregon. I'm 0 for 5 right now.

Sid

There is a machine shop in Marshalltown, Iowa that deals a lot in the old engine blocks, especially flat heads. They had a shed packed full of flat heads at one time. I am sure they would be willing to ship you a good short block. The name of the machine shop is Benskin Motor Service. Might be worth a shot.

Most likely the pistons aren't stuck to the walls, more likely the rings. I've always had good luck with Mystery Oil, just let it set for a week, then tap-tap with a hammer & chunk of brass rod

Next engine, before you try any other goop, pour some veterinary iodine in the cylinders. It helps to get the bores vertical so the iodine goes all around the piston top without using gallons of the stuff. Of course, you can only do four holes at a time this way.
I've had really bad rusted pistons free up overnight doing that. Sounds strange, but an old dude who worked in a farm museum showed me the trick, he said it rarely fails, and when it does, the engine was seized solid before it rusted!