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By 55ebird - 10 Years Ago
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I'm tearing down a 312 block and there is one piston that will not come out. I've tried hitting it out the top, the bottom. I've used a wood block, a steel chisel and lots of PB Blaster. The piston is in #2 cylinder and is at the TDC position. Any suggestions would be greatly appreciated.
Steve
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By Pete 55Tbird - 10 Years Ago
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Can you tell if the cylinder is rusty? If that is the problem you could turn the block upside down and fill the cylinder with a weak phosphoric acid ( like COCA COLA ) and give it time and some occasional heat. Pete
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By 55ebird - 10 Years Ago
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Pete, It doesn't look rusty but it sat outside, without heads, for many months. I'll try the Coke.
thanks
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By Dobie - 10 Years Ago
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If all else fails or you're in a hurry you can cut out the top of the piston with a hole saw, then carefully collapse it enough to get it out.
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By Pete 55Tbird - 10 Years Ago
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Steve. Another thought to free the piston. After soaking a couple of days put the cap on the rod and use a wooden rod to try to twist the piston side to side and free up the rings. Pete
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By 2721955meteor - 10 Years Ago
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tight piston 312,just had same isue 292,drilled several holes around the piston,both sides of the wrist pin. 1/2 in holes. then gave it a spach withe hard wood block and a 5lb hamer,piston broke up enough to come loose,tho the water damage made 1 sleev inst necesarey. cliff
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By 56_Fairlane - 10 Years Ago
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Flip the engine with the crank side up and try filling the bottom of the piston with dry ice pieces and let it sit for a while. The piston might shrink enough to pound out.
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By weasel - 10 Years Ago
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The boys over in the marine business, recommend a mixture of acetone and auto trans fluid, mixed half and half. Only drawback they say is it's a volatile mixture so take care.
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By 314 - 10 Years Ago
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since its at the top drive it down first.just enough to break it free.if you hit it hard enough it will go down.use a mall not a hammer.
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By steinauge - 10 Years Ago
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I have had good luck with heat, the penetrant of your choice and a piece of fence post about 2' long that is close to bore size.After a few days of heat and penetrant put the piece of fence post on top of the piston and hit it with a sledge hammer.If you are at .TDC you will need someone to hold the piece of fence post.Once it moves at all you have it,just keep moving it a little at a time.
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By 55ebird - 10 Years Ago
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Victory at last!!! Got the stuck piston unstuck and out of the cylinder. No visible damage to cylinder wall. The suggestions from forum members were most helpful. I started with Pete's suggestion of a weak phosphoric acid. Used a diet Pepsi and filled the cylinder. Let set for a couple weeks. Resumed pounding and got my first movement, about 1/4 ", but no more. Pounded for a month with no results. I was using a 5 lb hammer and a steel "drive." Also used a piece of oak and could drive the piston down a 1/4" but no more.
I was focusing my pounding on the wrist pins (from below) as to not break the top of the piston. In final frustration i began to hit the top of the piston (from below) and when the piston cracked and separated, at the level of the rings, it came out the top of the cylinder.
Thanks again to all the forum suggestions.
T  
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By Park Olson - 10 Years Ago
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I just got to this post,,,the piston looks pretty dry, what sort of solvent stuff were you using ?
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By 55ebird - 10 Years Ago
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Park,
I tried to use PB Blaster. I turned the block upside down and filled the cylinder with it. Let it sit for weeks. No real seepage into the piston/cylinder area. I also tried to force the PB Blaster down into the cylinder from the top. I think the piston/rings were fused tight and not letting much seep alongside the piston. I was amazed that there was no visible scaring or on the cylinder walls.
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