How to install pistons and check oil clearance
I told you I was a Cr-V enthusiast, and by god, I'll show you. This is my motor I've been working on for my project car. It's a B20Z bottom end with a b16a2 head. In this tutorial, I'll be explaining how to put pistons into your block, and how to check your rod bearing oil clearances.
Estimated Time: 20-ish minutes per cylinder
- Rubber hammer
- Piston ring compressor
- Assembly Lube
- 7/16ths 12 point socket
- Half inch Torque Wrench
- Half inch Ratchet
First thing we're gonna do is lube up your tools/parts. Put some assembly lube on your fingers and lube the cylinder walls, as well as your piston rings, and the piston ring compressor.
This is the piston ring compressor. You're going to be pushing the piston through this, so it's important that the walls are slick with oil.
Drop some lube onto the wrist pin, make sure everything that's going to be moving is oiled. During first start up, this is the only barrier until your oil pump begins pumping oil. There is never too much lube ;)
Here are our piston rings. There are four in this case. An upper, a mid ring, and then the two oil control rings that sandwich your oil scraping ring. The purpose of piston rings is to seal the combustion chamber while allowing the piston to still move, as it expands and contracts in the cylinder. You do NOT want them open like this. The exhaust gasses can pass right down the cylinder. You want the openings of each ring opposite of each other.
Turn the rings in the groove until none of the gaps are open. See in the photo, the top ring opening is away from the middle ring opening? That's good.
Open up your piston ring compressor and slip it over your piston. You want to keep it centered and even as you tighten the compressor down.
You slip the key that fits into this square hole and turn it to compress the walls of the ring compressor. Go slow! I found that giving the compressor a squeeze with your fingers helps evenly compress the rings.
I leave the pistons skirts exposed to make it easier to center the piston in the block.
Time to install the bearing. I'm using ACL bearings. Honda actually has different sized OEM bearings, your code is stamped on the oil pan mating surface on the block. It uses colour and letter codes to determine the specific bearing used. I'm using standard sized bearings. As you can see on the rod end, there is a little indent. That is how you align the bearings.
Here is the bearing. Do NOT lubricate the side of the bearing that fits into the slot. They need to go in dry. Any type of lube may cause a spun bearing!
Align the indent, or TANG, into the slot and gently push the bearing into the rod. You might hear a little snap, but go slow and only use your hands.
As you can see, the bearing is even on both edges. That is very important to prevent a spun bearing. You do NOT want a spun bearing. I know, I know, the crank is spinning so why's it bad if the bearing spins too? Think about it. Imagine when rotating your wrist, the skin kept going. Once you've fit the bearing, put the assembly in the block.
Drop it in, and using the handle of your rubber handle (Assuming it's not steel), hold the compressor to the block and tap the piston into the bore. If something seems wrong, STOP. I have had times where a ring popped out preventing the piston from moving down.
Viewed from the bottom, you can see the end of the rod above the crank. This is not a good position for the crankshaft. I rotate them so the journal is in the bottom of it's stroke, so you can easily control the placement of the journal onto the crank. Do NOT hammer it onto the crank. Once you get it close, flip your block over on your stand and pull the rod onto the journal. You could have lubed the bottom half of the journal and bearing because the plastigauge is not touching that part of the crank.
Once you've snugged up your rod to the crank, it's now time to check the oil clearance! This is an important step, especially if you're working with a stock motor. You have to buy new bearings to find out if you need oversized bearings. In my case, because the crank got polished and they found the diameter was perfectly in spec, and they're new rods, there's a good chance our clearances are fine.
Cut yourself a piece of plastigauge. What is does, is it compresses between the bearing and journal surface and occupies the space that oil would. You then measure the thickness of it to determine your oil clearances.
Lay that bad boy on your cleaned crank journal. I use brake clean on a coffee filter, it's lint free! The last thing you want is anything abrasive on this surface.
Install the bearing on the rod cap. Same idea, make it flush with the cap. Keep it clean, and for now, don't oil it.
In my case, I had to use ARP Lube for my bolts because these are ARP bolts! In my case, these are required. The bolts used in OEM rods are the same kind of bolts in a D series motor, which is bad news for me.
Here are the torque specs for my rod bolts, However these are ARP bolts so they have a different torque spec.
In my case, these bolts get torqued to 43 pound feet of torque. I combine these numbers and first torque the bolts to 14 pound feet of torque and then move on to the 43.
Torque the nuts evenly and slowly. You don't want to be all herky jerky with the torque wrench. You'll hear a nice click and then you're there. Don't try to top up on torque like you do at the pump.
Remove the bolts. Do NOT ROTATE THE CRANK. You'll smear your plastigauge and then you won't get a good reading. I gently tapped the piston down to unseat the dowel pins in the rod cap, while holding the cap to prevent any kind of force on the plastigauge.
As you can see, using the gauge provided, our clearance is between 0.0015 and 0.002.
Here are the oil clearances for our motor. IIRC, the range was 0.008-0.0015, with a 0.002 inch maximum oil clearance, and we are well within those ranges!
Clean the plastigauge off your journal and bearing cap and lube it up. Can never have enough lube, I'm telling you!
Place your cap back over the journal and torque it all down, and then you're done! Go on to the next one, get going! This motor isn't going to build itself!