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Hi! I have removed the 215 (?) from my 48 chevy 2 ton because engine was stuck. Now I am down to the bare block with one piston stuck mid stroke. I have used generous amounts of penetrating oil on the piston and rotated upside down and lubricated bottom of cylinder as well for a week or so.
Can anyone suggest any method of coaxing that last piston out, preferably without damaging the piston, connecting rod or cylinder too badly?

Probably 216, but could be an early 235 (measuring the bore will confirm), but that really doesn't matter for the problem at hand. Not all penetrating oils work the same... My go-to is Kroil, but frankly, a 50/50 mix of ATF and Acetone probably works as well. Just be carful with the Acetone, if you use that, since it is very flammable. Some gentle persuasion with a wood block and hammer - in both directions - may help, also.

Sometimes it just takes a long time to work, so patience is another necessary ingredient.

Hope this helps.

Doug

The cylinder will probably need to be rebored in any case. If the crankshaft is removed and the rod hanging free, use a 2x4 or similar on top of the piston and nudge it loose with a hammer, stopping before the piston hits the bottom, then tap it back out the top. The piston ring grooves will likely be damaged as well, but since the cylinder will need to be rebored you'll need new pistons anyway.

Just spitballing here but, try Evaporust. Once the rust is gone use one of the products referenced above and try tapping the piston again.

Bolt a piece of 2" square tubing across the top of the cylinder with a couple of head bolts, and use a piece of 3/4" all thread rod and a nut welded to the tubing to put some down pressure on the piston. Tighten the bolt against the top of the piston, smack the top of the threaded rod with a hammer a few times, "Rinse and repeat". Keep the cylinder well-soaked in penetrating oil while you're persuading the piston to move. Count on boring the engine oversize to get rid of the rust pits. I'd suggest putting a set of standard bore 235 aluminum pistons in rather than going back in with the heavy cast iron 216 pistons. The lighter weight 235 pistons have the same compression height and wrist pin size as a 216. You'll need to bore the cylinders .0625" oversize, which will clean up any deep rust pits nicely and give you 224 cubic inches in the process.

A 216 will have a 3 1/2" bore size, and a 235 will be 3 9/16". The stroke is also different on the 235. A quick measurement of a piston will tell you which engine you're dealing with.
Jerry

I like that idea also. Evaporust is great stuff.

I bought an old bus for a song one time back in the era when hippies did such things. I was the mechanic for a private school. The engine had been sitting on the ground next to it in the rain with one head off for over a year. The school administration considered it junk. Perhaps there was enough nickel in a 322 Lincoln V8 truck block to inhibit rust but I was able to dry it out in the shop and fill the cylinders with penetrating oil and wait - like weeks or maybe months. Anyhow after a time I was able to pull the other head and the crank and coax the four stuck pistons out of the bores. There was not enough ridge at the top to hurt the rings or pistons as they came out.

I carefully removed the rings and cleaned the grooves one at a time and reinstalled the rings. Then honed the bores clean, washed them and dismantled the rest of the engine to clean everything. Then I reinstalled the pistons and rods, then the crank, found a good head, torqued everything down and put the engine back in the frame. Same bearings, rings, everything. New gaskets though nearly broke the budget. I was poor in those days. I charged the batteries pushed the starter button and it ran, ran well, no smoke, no blow-by. So for a hundred bucks I had a '52 Kenworth 58-passenger school bus that I lived in for several years. Just shows what you can do if you take your time and you're careful.

I just fought the same issue with a 235. Kroil worked for me. It still took about a week of soaking.

John

If all else fails take a good solid wood 4X4 and trim the corners as necessary to fit comfortably in the cylinder. cut the length to maybe 6 or 8 inches above the block. Or find a good solid wood post of the appropriate diameter. Hit the wood on top of the piston with a SLEDGE hammer until the piston goes down maybe a half inch, then clean inside the cylinder above the piston as necessary.

After the piston moves down it should be loose. take a metal rod and hit on the bottom of the piston in different places, sparing the connecting rod to remove the piston. As mentioned you will likely need new pistons anyway.

I said if all else fails use this method. You can ask me how I know this.

Last resort- - - - -drill a series of 1/4" holes around the perimeter of the piston a little inboard of the rings, and break the center out of the piston with a BFH and a punch. Then the remaining piston material can be chipped out with a hammer and a punch. In the very unlikely event the block doesn't have to be bored, a few of us have plenty of cast iron 216 pistons we'll be happy to give you just to get rid of them! Just tell us the bore size- - - -standard or overbored.
Jerry

This is another inane question. I don't have any idea about. I'm completely out of NOS 235, 292 and 216 pistons. My good used stock is also empty except for a standard 216. Please tell me the difference between the 216 & 235 standard piston? Can a person bore a 216 so that a 235 piston will fit? Doc.

Yes, see Jerry’s post 4-6 or so before this one.

216 and 235 pistons have the same wrist pin diameter and compression height. The only difference is the bore size. Standard bore 235 aluminum pistons can be fitted to a 216 block by boring the 216 1/16" oversize (0.0625") The advantage to doing that is a lot less stress on the 216 Babbit rods- - - -the lighter weight aluminum pistons don't pound the Babbit out and increase the oil clearance as much as the cast iron pistons do.

The "sneaky Pete" 216 I'm building is going to have a 235 crankshaft and pistons in it, a "Corvette 235" cam, pressure lubricated rod bearings, and 292 connecting rods to compensate for the lower block deck height. It will also have an oil pump for a 250, and the full-circle lip seal at the rear main bearing. From the outside, it won't look any different than a standard 216.
Jerry

Jerry, Haven't you been building that engine for over a year now? When are we going to see the actual write-up with photos??

Kevin, don't poke the bear!

One minor setback was finding somebody to grind crankshafts "my way". Along the way, I have acquired not one, but two Storm-Vulcan crank grinders, and modified the wiring of my shop to provide the 3-phase power to run one of them. The other one was bought as a :"parts machine" that appears that it might have less wear and tear on it than the "complete" one I bought from a builder of NASCAR billet cranks for four times the price of the first one! Of course, with the power upgrade, I'll also be able to finally put three other pieces of equipment to use that also need 3 phase!

There are also three of four other engines in progress, all of which require non-standard crankshafts. I figure by the time I would have paid for multiple custom-dimension cranks, the grinding machine will pay for itself. There's a 300-something cubic inch "261" in the works, a 258 cubic inch "235", and a super-short stroke "305" V8 that should run 8K RPM or more and stay together. That one's also getting a roller cam and a rev kit.
Jerry

OK I understand. You've got a lot of irons in the fire. Waiting anxiously for your report.

Cylinders 1 & 6 rusted tight. Penetrating oil for a month no help.

Used Eastwood Rust dissolver for a day, drained & replaced 2 times. Then some gentle heat (torch) and let the chemical burn, twice. https://www.flickr.com/photos/mikeybs51chevy/50766493906/in/dateposted-public/

Then 2x4 then started moving back and forth by tapping with block and hammer on different pistons.
In about 20 min had crankshaft spinning.

In machine shop now, certain boring due to corrosion.