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Replacing Piston Rings......HELP Please.


Phlebmaster

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Don't want to say anyone is wrong on ring gap orientation, but piston rings DO ROTATE in operation. 2-cycle engines actually have 'stop pegs' in the ring gaps, specifically to prevent ring rotation. 2-cycle engines can break the rings on port edges if allowed to float around.

Here's an eye-opener.

http://www.diagnosticengineers.org/journal_%20articles/Ring%20Gaps%20vs%20Knowledge%20Gaps.php

 

Flame suit *ON*

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You don't want them lined up on initial install because if they DON'T rotate (and yes, I know they normally do) you end up with a weird wear pattern.

 

Now, 3-piece oil rings, which are still used today, absolutely need to be staggered.  They rotate as a unit, not independently.  You don't want the gap of the expander lining up with the scrapers.  It can make the expander "jump" and become useless.

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Paper or cardboard?????? While this will 'work' it's surely not a permanent fix. Brass shims were used in the 'old days' to correct bearing clearance but never recommended in today 's close tolerance higher power engines.

 

 

Chevy owners.... (shakes head in wonderment)

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For the love of god and ratsun, please clock your rings appropriately to prevent heavy blow by.

 

I do mine 180 degrees of eachother if no spec is given by the ring manufacturer.

 

Also, a pair of ring pliers would be great , helpful for installing them without breaking them. Practice with the old rings to get used to handling them. While your in there replace bearings , there cheap and tighten up the clearances.

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During lower engine class my instructor explained why older engines had to have the ridges reamed.

 

They used to use high tension rings, which are generally made of cast iron. This wears the block faster, and since the rings don't go up to the top of the cylinder, it leaves a ridge of unworn metal.

 

Most engines made after the mid eighties use low tension rings. You can compress th em fairly easily by hand. I forget what they are made of. I want to say CrMo.

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Good modern rings use a stainless top ring, ultra-low tension, and about 1/4 the thickness of what you got in a Chev 327, Ford 289,  or similar of the era.  The 2nd ring is typically cast, oil control rings come in 2 varieties also ultra-low tension.  

 

With the quality of Datsun blocks, I'd be surprised if there was ever a ridge present with any amount of mileage, using any style pistons and rings.  Its far more likely to see a gouge in the bore wall at the bottom of the stroke.  Its not present until you give the cylinder walls a quick hone, and a dead spot appears on the passenger side of the bore from piston tip.  

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