I have a 1987 Dodge Dakota, 3.9 liter, Carb, California model. I dropped the value face into the Number 6 piston and of course I needed another piston and head. Don't ask how this happened because I don't wish to discuss my stupidity. The first answer given is very incomplete.
There are two logical ways to remove a piston: 1) from the top of the bore, or 2) from the bottom of the bore. If you attempt to remove the piston from the top of the bore the crankshaft is in the way; note it's also in the way if you attempt to remove the piston from the bottom of the bore; so regardless which way you pull the piston you will be required to required to remove the oil pan, which is a problem in itself. I attempt to do this at a pick-&-pull yard with the engine in the vehicle. This could not be accomplished without first raising the engine because the oil pan will not clear the oil pump with the welded frame member crossing under the engine. THE ENGINE WILL FIRST HAVE TO BE LIFTED TO REMOVE THE OIL PAN.
Once the engine is lifted, I could remove the Oil pan, drop the crankshaft, and remove the piston and connecting rod. On all engines [with any notable mileage] there will be a carbon ring on the top of the bore, so unless you first scrap this deposit off, it will be easier to drop the piston [down] out of the bore. It is possible to remove the piston [down] without first removing the head, but I would not recommend if you are using this engine in the rebuild, because the top ring of the replaced piston may [probably] will make contact with the existing carbon deposit on the top of the bore and may [probably] will damage it; so if you are using the same block you may as well do it right and remove the head before dropping the piston. Remember first drain the water out of the head using the drain plug(s) located on the side of the header before removing the head.
OK, the moral of this story is you will be required to lift the engine and if you are required to lift the engine you should think about remove it from the vehicle since it’s a lot easier to rebuild an engine on a stand than if it's left in the vehicle.
There are two logical ways to remove a piston: 1) from the top of the bore, or 2) from the bottom of the bore. If you attempt to remove the piston from the top of the bore the crankshaft is in the way; note it's also in the way if you attempt to remove the piston from the bottom of the bore; so regardless which way you pull the piston you will be required to required to remove the oil pan, which is a problem in itself. I attempt to do this at a pick-&-pull yard with the engine in the vehicle. This could not be accomplished without first raising the engine because the oil pan will not clear the oil pump with the welded frame member crossing under the engine. THE ENGINE WILL FIRST HAVE TO BE LIFTED TO REMOVE THE OIL PAN.
Once the engine is lifted, I could remove the Oil pan, drop the crankshaft, and remove the piston and connecting rod. On all engines [with any notable mileage] there will be a carbon ring on the top of the bore, so unless you first scrap this deposit off, it will be easier to drop the piston [down] out of the bore. It is possible to remove the piston [down] without first removing the head, but I would not recommend if you are using this engine in the rebuild, because the top ring of the replaced piston may [probably] will make contact with the existing carbon deposit on the top of the bore and may [probably] will damage it; so if you are using the same block you may as well do it right and remove the head before dropping the piston. Remember first drain the water out of the head using the drain plug(s) located on the side of the header before removing the head.
OK, the moral of this story is you will be required to lift the engine and if you are required to lift the engine you should think about remove it from the vehicle since it’s a lot easier to rebuild an engine on a stand than if it's left in the vehicle.
