Piston Primer: How to Properly Install Pistons

Posted 04/30/13 by Wayne Scraba

Last updated on 02/22/2022

You’ve seen it—somebody trying to install pistons and ending up with pinched or broken piston rings or so much oil in the bore their shoes are drenched. It doesn’t have to be that way if you use the easy-to-follow procedure outlined in the photo captions. Happy piston installin’!


		
				
		
		

		
		

		
		

		
		

		
		

		
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Wipe the cylinder bores with a clean, lint free towel and apply a small amount of conventional (non-synthetic) oil to the walls. Apply a liberal amount of oil to the wrist pins and piston rings as well. You don’t need to drench the piston in oil—use enough to lubricate the rings as they pass through the piston ring compressor. No need to dunk the piston and ring assembly in a quart of oil!
There are two basic types of ring compressors. Expander models clamp over the piston and are tightened in place. Tapered compressors progressively tighten the rings as the piston is pushed through the tool into the bore. Whichever one you use, liberally coat the compressor with oil. Again, it doesn’t have to be dripping wet.
Rotate the crankshaft so the rod journal for the piston you’re installing is at Top Dead Center. Place the piston/ring compressor combination over the cylinder bore. Always do the following before sliding the piston into the bore:
• If the piston is domed, the dome should be to the outside of the block 
• Check that the chamfer on the connecting rod (and rod bearing) is facing the fillet radius on the crankshaft 
• Make sure the oil rings’ expander ring end gaps haven’t overlapped
• Cover rod bolt ends with protectors to prevent crank damage during installation
• Coat the connecting rod bearings with assembly lube
It’s often possible to hand-push the piston and rod assembly into the bore, guiding the rod so that it falls in place over the crankshaft rod journal. Other times you will need to very light tap the assembly in with the handle end of a clean plastic hammer. If you need excessive force to push the piston through the ring compressor into the bore, it usually means the oil ring expander rails are overlapped.
Rotate the engine on the engine stand. Coat the bearing in the rod cap end with assembly lube and install. You can install the rod cap nuts and torque to specifications at this point, provided you’ve checked the bearing clearances. Repeat this sequence on the rest of the piston/rod assemblies.
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Tools Required

[important]Which complicated install would you like to see us break down next? Please tell us in the comments section below.[/important]

Comments

9 responses to “Piston Primer: How to Properly Install Pistons”

Video: How to Install Piston Rings - OnAllCylinders says:

January 28, 2014 at 4:33 pm

[…] You may also want to read our post detailing how to properly install pistons. […]

Reply
Rich says:

June 2, 2017 at 4:56 am

Could someone please tell me what type of Piston Knocker Pat Topolinski uses to install pistons and who is the distributor of that tool?

Reply
OnAllCylinders says:

April 11, 2018 at 4:08 pm

We haven’t been able to track that information down, Rich

Reply
dave says:

October 20, 2018 at 6:38 pm

It worked but now my piston flew through the engine and smashed my balls…

Reply
Nik says:

February 23, 2019 at 9:58 pm

If your piston flew “through” your engine, it sounds like you’re definitely doing it wrong. Install your crankshaft first, a few inches of fuel hose on each rod bolt, to protect your crankshaft rod journals on your crankshaft and to guide your rod onto your crank.

Reply
Eddie L Stokes says:

May 7, 2019 at 9:30 am

Thank You!!!

Reply
keith schaefer says:

July 2, 2020 at 6:31 am

I have a SBC 350 my ring gap is 0.0035 do i need smaller rings or bigger rings

Reply
atmosferis says:

July 29, 2020 at 3:50 am

Gamblers are a different breed. There’s a point where they seem to know when a bluff has gone too far, when it’s time to fold their hand and live to fight another day. The art of building racing and high performance engines involves often pushing engines near their limit. The difference is a good engine builder knows how to stack the odds in his favor. Is reusing pistons worth the risk? Here’s how to make an informed decision.

Reply
Jeff says:

April 27, 2022 at 10:28 am

“If the piston is domed, the dome should be to the outside of the block”

#1, Are ALL domed pistons ALWAYS facing that way for EVERY engine?

#2, For an inline engine, which way is the outside?

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Piston Primer: How to Properly Install Pistons

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9 responses to “Piston Primer: How to Properly Install Pistons”

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