Really, Really Stuck Pistons

I'm looking for fresh ideas on removing stuck pistons for a rebuild on my GMC "Twin Six" V12. Someone left the plugs out a long time ago and the cylinders got moisture in them. I think the cylinders are going to clean up at .030 thanks to the high nickle content of the block but I don't want to damage them any further getting the pistons out. It took me almost 7 hours to get the first one out, in pieces, and I only smacked my hand twice with a 5 lb. sledge. I know I only have 11 more to go but I would like to know if someone has an idea that I haven't thought of yet to expedite this process a little. I built a little puller using 1/2" all-thread and tapping into the top of the pistons but the aluminum will only hold so much pressure before the threads pull out. I've soaked them with all kinds of penatrating oil and rust-buster. I also used limited heat to no avail. Any ideas?

 

if you dont have any use for the pistons just shatter them with an air hammer

 

Instead of thread tapping the holes in the pistons, if you have easy(ish) access to the inside of the piston, maybe you could drill 2 holes on opposite ends of the piston and stick a length of your ready rod through each hole and put a big washer and nut on the ready rod inside the piston. Its basically the same puller idea except you wouldnt have to thread into the piston and you have 2 anchor points.

Cool engine choice. What is it going into?

 

I've heard of people pouring boiling oil into the cylinders to free the pistons.
Sounds a bit dangerious to me tho, so be careful!

Also I've heard of soaking the motor in a bath of diesel fuel for a few weeks.

Good luck!

 

How long did you soak it with various penetrants? I've had good luck using a 50/50 mix of ATF and solvent. Fill up each hole, and wait. You'll eventually start getting fluid past the rings. Worst I ever had took a little over a week. A good solid tap using a block of wood and a hammer on the piston top helps too. Good luck. What are you gonna put that beast in?

 

The boiling oil thing will work. I had an OLD TIMER show me this trick,thought he was full of shit but it worked. And remember that you can knock the piston down in the hole easier than you can pull it buy all the rust. Knock it past the rust sand the rust or buff it and then pull the piston past it.

 

pepsi helped on a 283 once, but one of the pistons was absolutely fused to the bore. Had to bust it to peices to get it out.

 

It's eventually going in a '50 GMC COE coupled to a 4L80E transmission. The pistons have been soaking for over a month. I think one reason these are so tough is that they have a steel top ring groove insert cast into them and they are very thick. My air hammer wouldn't hardly faze them. The 60 degree vee and big rods make it more difficult to get a good lick on the bottom side of the pistons than normal. It seems like heat would help, but I don't want to crack the bores. I like my skin so I don't know about the boiling oil yet, maybe a last resort.

 

I'm not sure if I can get the crank out to drive the pistons down any. There are a couple of rods in a bad spot to get to right now, but it may come to that.

 

I like Briggs thinking. But instead of using washers, use a peice of angle iron or something that won't give much, from one hole, across the piston pin, to the other hole.

Other thoughts -

Rust disolver.
The stuff in the blue bucket, like $450 for 5 gallons. It will make valves rusted solid into the guides fall out after soaking over a weekend
The rings are rusted to the bore, most likely, so pulling the piston out intact without first attacking the rust is not likely to be successful. If you can get half of the engine submerged at a time, leave it for a weekend (or even a week), and then beat on the pistons - they will probably fall out. If you can't submerge the engine, you could use a pump, and constantly pick up what leaks past the piston back into the cylinder above it to soak it that way.

or
Many hours carefully hand-hammering to break up each piston without dinging the cylinder wall.
or
remove it with a boring bar. There are really cool old school single-cylinder boring bars for in-frame overhauls out there. Or you could build one. Make a plate to bolt across the cylinder using 2 head bolts, with some sort of fixture to hold it square, but allow it to go up and down. Most 1/2" drills have a round area just below the chuck for mounting a handle, and this is a good place to mount it in your fixture. A benchtop drillpress is perfect, but you'll probably have to make it not a drill press anymore, so use a raggedy garage sale or cheepo China one.
Punch out the center of the piston with a hole saw.
Make a boring bar - a cutter on the end of an arm (adjustable length) sticking out sideways from the part you mount in the drill.
Now you can cut the top ring land off, peel out the top ring, cut off the next ring land, peel off the ring, once the rings are gone, the rest of the piston will probably move without a lot of force. If not, with that much piston gone, beat directly on the piston pin (now exposed across the center from the top) until the piston collapses in on itself or the steel pin bosses break away from the aluminum.
At this point, the rest of the piston should be able to be removed easily.
Once you have made the fixture (or borrowed the portable boring bar), and learned on the first piston removed this way, the rest is substantially less hard on your hands (and usually substantially faster) than the way you removed the first piston.
Just be careful that you never extend the boring bar far enough that it cuts on the cylinder wall. The centering doesn't have to be perfect, but the better it is centered, the less you'll have to worry about the boring bar hitting a cylinder wall.
OR
pay a machine shop about $100/ hole (around here) to do it for you.

 

And as someone mentioned the rust in the bore being in the way of pulling the piston up - good thinking, I forgot that. A ball hone will probably remove the rust with the least amount of random cylinder wall damage to throw off the boring later...

 

Mill a 4"x4" post down to the bore size on a lathe, cut to around 12" long. Put a coffee can or something over one end, stick the other in the bore. Whack on it with a big sledge.

If you can get the rods loose it will help a lot. And please post some pictures of this motor at some point, I'm sure lots of folks would like to see what these things look like.

 

it takes a while for one to freeze up that bad. it isn't gonna free up over night. be patient and soak it for awhile.

 

If you get desperate Muratic acid disolves alunimun Pool acid is a common source. that stuff is nasty grease everything else first nuteralize with baking soda and water solution after removing do outside and avoid fumes

 

Toolmaker's right, muriatic is the way to go. Wear a resperator, chemical gloves, goggles, have a garden hose handy, don't worry so much about protecting the iron, it will clean it up nicely. I'd go ahead and degrease before to make the most of it. And yes, neutralize with a baking soda/H2O solution when done. Sure beats breaking a bore in a priceless block!

 

If you're going to use the wooden post idea, make sure it's oak or some kind of hard wood. That way the shock transfers to the piston instead of just muushing the wood. Propane heat wouldn't hurt either.

 

I got a well and truly rusted-in piston out of a vintage motorbike engine many years ago with caustic soda solution. Please make sure I'm right on this before you try it, but I'm 99% sure it was caustic I used. I made up a 5 gallon drum full of the stuff and dropped the barrel and piston into the mix, left it for a few days and the piston turned to mush, while the steel barrel was perfectly clean, the soda had even cleaned 40 years of built up and burnt on grease off the fins.

good luck, Glen.

 

Torch, torch, torch... Melt the aluminum pistons out, they liquify way before that iron block will. No messing with caustic acid or gouging the walls with a chisel.

 

I've had very good luck with diesel fuel, especially if you give it some time.

 

Diesel fuel+time+rocking the crank+time+pecking on pistons+more time= unstuck pistons.

 

Thak it to a auto machine shop and have it hot tanked that should eat up the pistons. I have torched the rods to remove cranks . with the crank out you might make a frame jig and use a hyd jack and pressthem loose. Ive had good success using brake fluid on stuck pistons. OldWolf

 

Are the lifters in those really right there at the deck, or is that an optical illusion?

I have redone a few old tractors that were stuck really bad. Here's what seemed to work best. Turn the block so one bank of cylinders is straight up, then stick an old rag in each bore, and pour your favorite diesel/brake fluid/kerosene/used oil into each cylinder. The rags are your "wicks". Light 'em up, and let them burn. This will heat the block up slow enough so that you don't need to be concerned with cracking. Of course this works a lot better when you don't have pistons with holes in them, so not sure if you can get around that little issue. I guess you could bolt a head back on and heat it up this way from the bottom. You'd actually be exposing more of the piston to heat this way, so it might work.

One old John Deere that I freed up took a couple of days of this treatment before I could knock the pistons out, but enough heat/cool cycles should break them loose. Rotate block and repeat on other side.....

 

I've tried kerosene or mineral spirits. It should soak through. Watch out if you are going to use the torch method. !! I've also drilled several holes in pistons to weaken the piston so you don't have to hammer, and crack the piston up with so much force.

 

Where are you in Texas? Is it still cold at night? Use your solvents and heat lamps all day and roll it outside at night. The idea of making a fixture to attach to the deck is ok, but I'd make it stout enough to use a bottle jack to apply enough to break them loose. Be careful of how many chemicals you mix in this process especially if you add fire!

 

I have been told the easiest way to free up a stuck engine is to do it as cold as possible. Something about the aluminum pistons shrink smaller than the block.

 

Liquid Nitrogen, it will shrink them then you can just tap them out, with little or no force.

 

ive always used a 2x4 and a hammer to get them out of the old stuck flatheads. just soak the pistons for a few days get the crank out of the way and knock them out.

 

Mouse milk. This stuff is amazing. Well worth the money.

http://www.mousemilk.com/index.html

 

Last year I took the pistons out of six T engines that were in flood waters for many years and just plain stuck. First I try to get the crank out then clean the top and bottom of each piston, especially on the outside edges. Soak each bore with fuel oil top and bottom, and then once a day wack each piston with a 2 x 4 wittled down to fit. Use a LARGE mall. Of the six engine I broke only a couple of pistons and had the freed up in nine weeks. Also in the past I've used plain old water. If there stuck because of water it will also help freeing them up.
Pictures show the condition of engines when I found them.

 

I got a lead on this stuff earlier http://www.henkelna.com/cps/rde/xchg/SID-0AC8330A-7049ED9C/henkel_us/hs.xsl/7008_USE_HTML.htm

It is a new product being sold thru Loctite. I purchased two cans earlier today at $14.00 each from Fastenal (the only place that had any in stock).

I will be trying it later tonight and will post the results. I like the piston freezing concept.