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142 Guy · Apr 6th, 2022, 19:19

I am not quite 'getting' the heat / fire solution to piston removal. The aluminum piston has a higher coefficient of expansion than the iron block, so heat is just going to make for a potentially tighter fit. The sticking problem is caused by rusting of the rings to the bore, not sticking of the piston to the bore. If the plan was that heat would create a thermal shock that would fracture the bond, it is going to be pretty hard to get a really rapid temperature increase on the iron block in order to generate a thermal shock like you can do when you take a torch to a rusted manifold nut. Ditto with freezing, although a little liquid nitrogen or a dry ice mix might do the trick if the thermal shock doesn't crack the block.

I had the same issue on my B20E after it had been stored for about 15 years with no cover on the intake and exhaust. The cylinders with open valves breathe in atmospheric air due to ambient temperature changes and when the air has a high moisture content you have the inevitable condensation and rusting. For removal, I used a 4x4 piece of wood post (3.5"x3.5" actual with the corners trimmed to firm fit in the bore) and a 15 lb sledge hammer. I wrapped the connecting rod in a heavy towel wrapped with tape to keep it in place and protect it from damage when the piston popped out. I mounted the engine vertically on some wood blocks so that I was pounding down on the 4x4 and there was enough clearance below the engine to allow the piston and connecting rod to be ejected out the bottom safely. I think two hits did it and with the 15 lb sledge I did not have to hit really hard. In my case the rusting of the rings on the bore was bad enough that it required a 0.030 overbore. Depending on the severity of the rusting, there is a real risk that one of the rings may fracture and the end scratch the bore on the way out.

I did read of one person who claimed that by drilling the piston full of holes they were able to weaken it enough to facilitate removal. I can't vouch for that. It might be doable if the piston is stuck near the top of the bore. Much more difficult if the piston is very far down the bore.

Apr 6th, 2022, 19:19	#27
142 Guy Master Member Last Online: Yesterday 20:07 Join Date: Jul 2020 Location: Saskatchewan, Canada	I am not quite 'getting' the heat / fire solution to piston removal. The aluminum piston has a higher coefficient of expansion than the iron block, so heat is just going to make for a potentially tighter fit. The sticking problem is caused by rusting of the rings to the bore, not sticking of the piston to the bore. If the plan was that heat would create a thermal shock that would fracture the bond, it is going to be pretty hard to get a really rapid temperature increase on the iron block in order to generate a thermal shock like you can do when you take a torch to a rusted manifold nut. Ditto with freezing, although a little liquid nitrogen or a dry ice mix might do the trick if the thermal shock doesn't crack the block. I had the same issue on my B20E after it had been stored for about 15 years with no cover on the intake and exhaust. The cylinders with open valves breathe in atmospheric air due to ambient temperature changes and when the air has a high moisture content you have the inevitable condensation and rusting. For removal, I used a 4x4 piece of wood post (3.5"x3.5" actual with the corners trimmed to firm fit in the bore) and a 15 lb sledge hammer. I wrapped the connecting rod in a heavy towel wrapped with tape to keep it in place and protect it from damage when the piston popped out. I mounted the engine vertically on some wood blocks so that I was pounding down on the 4x4 and there was enough clearance below the engine to allow the piston and connecting rod to be ejected out the bottom safely. I think two hits did it and with the 15 lb sledge I did not have to hit really hard. In my case the rusting of the rings on the bore was bad enough that it required a 0.030 overbore. Depending on the severity of the rusting, there is a real risk that one of the rings may fracture and the end scratch the bore on the way out. I did read of one person who claimed that by drilling the piston full of holes they were able to weaken it enough to facilitate removal. I can't vouch for that. It might be doable if the piston is stuck near the top of the bore. Much more difficult if the piston is very far down the bore. Last edited by 142 Guy; Apr 6th, 2022 at 19:22.