To replace a car engine piston, start by removing the connecting rod cap and push the piston upwards and out of the cylinder block using the connecting rod. To install a piston, install the rod bearings, position the rings gaps, set the ring compressor, align the piston, and hammer it into position.
First, remove the nuts from the connecting rod on the number one piston. Using a punch, hit the end of the rod bolts for the caps to come off. Make sure to remove the engine bearing; otherwise it may get stuck to the rod journal. Put protecting sleeves onto the rod bolts. Keep the pistons from falling off by threading two long bolts halfway-in on either side of the cylinder, then twist a piece of wire between them to catch the pistons. Hit the piston using a wooden dowel, and it should slide right out.
Install the rod's bearing shell, put on the rod bolt protector, and make sure it sits properly on the rod body. Next, coat the ring gaps and the piston's skirts with engine oil, then position them accordingly.
Fit the piston into the ring compressor, and slowly tighten it, making sure the ring gaps sit in the right position. Place the crankshaft rod journal in the bottom dead center position, put the piston into the cylinder, and make sure the pistons face forward.
Using the hammer's rubber handle, hit the piston into the cylinder while checking to see if the oil scraper ring pops out or the compressor ring. Place the compressor aside once the piston is in. Tap the piston until it comes into contact with the crankshaft, and then proceed to install the rod cap.