The objective of this procedure is to show you how to install the pistons. Once pistons have been in stalled, use a torque wrench to tighten all bolts and nuts. After you have torqued all of the rod journals, leave the wrench on the final setting and go through every bolt once more.
Part 1. Preparation and safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection - such as rubber gloves and barrier cream
- Respiratory equipment - such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- Use a high pressure assembly lubricant to protect the bearings during the first few critical moments after start-up, until the oil pressure stabilizes.
- Use a torque wrench to tighten all bolts and nuts.
Part 2: Step-by-step instruction
- Install rod bearings
Take the appropriate rod bearing half from the storage bin, wipe any residual oil off of the rod and the back of the bearing and install the bearing shell.
When the engine starts up for the first time, the rod bearings are subjected to an extreme amount of stress while there is no oil pressure. Make sure that you use a high pressure assembly lubricant to protect the bearings during the first few critical moments after start-up, until the oil pressure stabilizes.
After a liberal coating, put on the rod bolt protectors. Make sure that the protector boots seat all the way to the rod body. Also double check that the bearing shell is fully seated in the rod.
- Set position of ring gaps
To set the positions of the ring gaps in the piston, start by putting a few drops of engine oil along each groove. Next grasp all the rings together and spin them around to spread a light coating throughout the rings and grooves. With a clean paper towel wipe any large drips and spread a light coating evenly over both skirts of the pistons as well.
Start on one side of the block, and all the ring gaps should be oriented the same way. The top compression ring gap should be here. The 2nd ring gap is located opposite the top ring at this position. In the oil ring groove, the point where the wavy expander ring butts together should line up with the gap in the top ring. Then hold the expander ring with a thumb and finger tip and slide the oil scraper rings so that one is in this position and the other is in this position. Each should be about 45 degrees to the left or right of the 2nd ring gap.
- Set ring compressor
If you try to slide the piston into its bore now, the rings will stop it from sliding in. To install each piston, we need to put it in a ring compressor.
There are a lot of different ring compressors available. The ribbon style compressor is the least recommended as they are not easy to use and they are more likely to break rings. If this is all you have, just be very careful and tighten slowly.
This and any other type of compressor can start to get crooked while it is being tightened. With any compressor, it's possible to pinch a ring in its groove and break it. This means you have to buy a whole new set of rings just to replace the broken one.
To reduce that risk, use a quality ring compressor such as this universal style.
With any type of compressor fit the piston in and tighten the compressor until it's just holding the rings. Square up the compressor and look down inside.
As you slowly tighten the compressor, make sure the ring gap positions stay where you want them and rock the compressor slightly left and right to make sure that the rings aren't caught on the edges of their grooves. When the compressor is about to pinch tight against the edge of the piston, it's ready to go into its bore.
- Position piston in cylinder
Check to make sure that the crankshaft rod journal is in the bottom dead center position. Also make sure the forward mark on the piston is facing the front of the engine.
Once the piston is in its bore, it'll be square with the block. With the compressor on the deck of the block, tap on the edges of it so that the compressor sits square to the block on all sides. Now tighten the compressor until it pinches tight on the piston. If you have a compressor with a hose clamp, loosen the tension a half turn just to release some of the squeeze on the piston.
Rotate the compressor and make sure that it's sitting square on the deck and that it's perpendicular to the block itself. Look up into the cylinder from below, and slide the connecting rod over so that there is some clearance between it and the crank throw as you hammer in the piston.
- Hammer piston into cylinder
Use the rubber handle of a hammer, or give the piston some solid hits with a piston hammer. You need to hit it hard enough to make it slide past the grip of the ring compressor, but if you feel even the slightest resistance, stop and check the compressor.
If you see any of the oil scraper rings popping out or even one the compression rings, stop and immediately pull the compressor off.
If you're tapping very slowly, a little at a time and a ring keeps popping out, try hitting a little harder in the beginning so that the piston will move quickly past the entrance at the block deck. Once the piston is in, put the compressor aside and just tap lightly to move the rod down till it contacts the crankshaft.
- Install rod cap
The protector boots will guide the rod into place on the crank and the rod will seat nicely on the rod journal as long as your bearing is still in place. Lubricate the cap that goes with the rod and look at the marks you stamped on the sides of the rod and cap to fit the cap on the right way. When the cap is in place, thread on the nuts and thread them hand tight with a ratchet.
- Check for cylinder wall damage
In Pre-Assembly you should have checked to make sure the cam didn't interfere with the rotation of the piston and rods. Now rotate the crank a few times to make sure that the rings aren't scarring the walls of the cylinder. If a ring broke while you were putting in the pistons, you should notice some scratching on the walls. Look all around the cylinders as you rotate and see if you notice any scratches that weren't there before. If you see a scratch, run your finger nail against it. If you're concerned that the scratch might be from a broken ring, pull out the piston and check the rings. If everything is in order, re-install that piston and move on to the next one.
- Repeat the process
Rotate the next rod journal to its bottom position and when the compressor is tight, tap on it again to make sure it's square with the block.
With the pistons on the first side of the block it's easy to slide the rod over to avoid hitting the throw of the crank as you hammer the pistons in. You should start to get a feel for how much force you need to get the rings to slide out of the compressor and past the block deck. If a ring pops out of its groove you should be able to feel immediately that the piston is stuck. Simply reset the compressor, square it all up and try again.
With each piston that goes in, you'll feel the rotation of the crank getting a bit harder to turn. There should be a steady increase in resistance as each piston is added.
- Adjust for the other side of the block
When the first side of your block has all of it's pistons in and rotating smoothly, you can rotate the block to the other side. Dust the cylinders and lubricate the walls with an even coat of oil.
Before the pistons go in on this side, set the ring gap positions on the pistons. On the second side, the positions are simply the reverse of the those on the first side.
As the pistons go in on this side of the engine, there is less room for them to clear the crankshaft throw and the rod of the piston that was installed on the other side. As soon as the piston rings clear the deck and you can move the compressor out of the way, make sure that you keep the rod that is being installed from hitting either the crankshaft or the rod from the other side of the block. As soon as the rod is just past the edge of the crank throw, you can press it against the crankshaft throw and push the other rod over to make room for the one being installed to slip into place.
Again, when it's time to put on the cap, make sure the marks on the cap and the rod are on the same side as each other. As you do your check rotations, always rotate in the direction that the engine will be operating once it starts up. Continue cleaning and lubricating the bearings as you go. As the last few pistons go in, the crank will become more difficult to rotate, however, it should still be possible to rotate it with one hand, even if the engine has a rope seal that pinches on the rear of the crankshaft.
- Torque rod bolts
Rotate the block upside down. Have a crank turning tool installed and rotate the first rod journal up. Set the torque wrench to the first of the three increments. Torque all four of the bolts for the first rod journal, set the wrench to the second increment and torque them again. Then set the wrench to the third and final setting and torque all four of the bolts.
Rotate the crank so that the next rod journal is facing up and then go through the three increments to reach the final torque setting on all of the rod bolts.
After you have torqued all of the rod journals, leave the wrench on the final setting and go through every bolt once more. If you miss any of them now, you won't be able to go back and check after the oil pan is installed.