How to Change Pistons

Installing new or reconditioned pistons in a car engine block is not too difficult. Still, you have to follow certain procedures to avoid damaging the pistons and cylinder bores. If you have some experience assembling main engine parts or want to learn something completely new, here you will acquire the right steps to successfully change the pistons in your engine. Make sure the block is securely mounted on an engine stand or laid on top of a sturdy workbench. So let’s begin.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Ridge removing tool
• Ratchet and six point socket set
• 8 to16 short pieces of rubber hose
• Hammer with wooden handle
• Lint-free cloth or rag
• Assembly lube
• Piston ring compressor

1. Remove the ridge from the top of each cylinder using a ridge removing tool before trying to take the pistons out. A thick ridge may break the piston as you attempt to extract it from its bore.

2. Turn the engine block upside down. Using a ratchet, loosen the connecting rod cap nuts 1/2-turn at a time, working your way from the center towards the front and rear of the engine block alternately until the nuts can be removed by hand. Make sure that all rod caps are properly marked so they can be reassembled with their respective connecting rod and piston assembly.

3. Remove the connecting rod caps and set them aside in a safe place. Now slide a short piece of rubber hose over each connecting rod bolt to avoid damaging the crankshaft bearing journals and cylinder walls as you slide the pistons out of the engine block.

4. Tap on the upper bearing surface of the connecting rod using the wooden handle of a hammer to push each piston-connecting rod assembly out through the top of the engine. Rotate the crankshaft by hand for access to the bearing surface of the connecting rods.

5. Clean the block, cylinder walls, crankshaft and connecting rod assemblies thoroughly before installing the new or reconditioned pistons back into the engine block.

6. Wipe clean each connecting rod and cap bearing surface using a lint-free cloth, then install the top bearings on each connecting rod by hand, making sure to respect any setting marks.

7. Place each ring in its respective piston ring groove, positioning each end gap at the correct intervals.

8. Apply a layer of engine oil around the piston, rings and cylinder walls. Lubricate the bearing face on the connecting rod with assembly lube.

9. Install a piston ring compressor on piston number one-the one closest to the front of the engine-making sure the compressor skirt sticks out at least a 1/4 inch at the bottom to guide the piston into the cylinder. Slide a couple of small rubber hoses over the connecting rod bolts.

10. Insert the piston and connecting rod assembly into the cylinder, securely seating the compressor ring skirt on the bore and making sure the top notch on the piston points toward the front of the engine.

11. Tap the top of the piston with the wooden handle of a hammer to slide the cylinder into its bore. Make sure the end of the connecting rod sits properly on the crankshaft journal. You should not feel any resistance as the cylinder slides into place; if so, make sure the piston rings are in place and nothing is obstructing the end of the connecting rod. Follow the same procedure for the rest of the pistons.

12. Install the bearings on the rod caps by hand paying attention to any setting marks, and then apply a thick layer of assembly lube to each bearing surface. Place the rod caps in their respective connecting rods following the torque and tightening sequence according to the service manual for your particular engine.

Tips & Warnings

• Some tools necessary for engine rebuilding may be quite expensive. For a one time job, go to your local auto parts store, chances are they will rent you the special tools you need to complete almost any job on your vehicle.
• It is a good idea to have the appropriate service manual to follow correct torque specifications and tightening sequence for your particular engine.
• Once you disassemble the pistons from the engine block, it is best to take all the parts-including the engine block-to a machine shop for a thorough cleaning and inspection job. A professional inspection and special equipment are necessary for needed rectification.
• Make an extra effort to ensure you are working on a clean surface and all parts are free of dirt and foreign particles as you reassemble the engine block. Even small dirt particles between engine parts can damage and reduce the life of your engine considerably.

[spartanic]

on 4/30/2009 This guide on pistons and rods is a must read: http://www.garage411.com/PistonsAndRods