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reinstalling old piston and rings

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jgeorge

11-21-2005 14:54:43




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When putting an engine back together with the old pistons and rings, not doing anything to the cylinders other than making sure the ring end gaps are staggered, are there any other precautions? I was told that the rings continue to rotate around the piston and not to worry about getting them back in exactly the same way they were taken out. Is this ring rotation true? What keeps the end gaps from lineing up sometime? Thanks for any advice.

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dr.sportster

11-22-2005 06:43:47




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
If you have the motor this far apart why just reassemble without rings?One thing not mentioned is after honing, cylinders need washing with detergent soap and water to clear the cross hatch of grit left from honing.In my opinion, to a certain degree, the piston is just a carrier for the rings.the rings do all the work of sealing.I have rerung extremly worn bores with used pistons and have had good sealing for a good while.A few passes with the dingleball hone to break the glaze should allow the new rings to seat.Wider than spec ring gap is an indication of cylinder wear.I was told in mechanics shool that rings rotate three times a minute in a running engine.I dont know that for sure but Im sure they do rotate.I would take sandpaper and break the glaze if you dont have a ball hone and at least replace rings.At least you will see a performance improvment from this.The end gap may line up in passing but as the rings further spin they unalign again.If not you would see a carbon spot in the top ring groove. Make sure grooves are carbon free by using a piece of broken ring if you have no groove tool.Follow installation instructions carefully top and second ring are two different designs in most motors.

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Ron in Nebr

11-21-2005 22:07:47




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
To answer your question directly without going much into why NOW would be a great time to put new rings on along with refinishing the cylinder walls- yes the rings DO rotate as the engine runs. Just space the gaps as far apart from each other as possible and you'll be fine. Since you mentioned ring gap I assume you've had the rings off the pistons. In addition to what the other post said about putting the rings back in the right grooves- also be sure you have them right side up. Rings are usually made with a specific taper on the outer edge to help them seal and control oil...and although used rings might have most or all of that taper worn off- you'd still want them right side up. Most rings have a mark, usually just a dot, stamped in 'em to show which side is up. Be sure not to twist the rings putting them back on the pistons- they should spin freely in the ring groove without binding.

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Ron in Nebr

11-21-2005 22:30:46




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 Re: reinstalling old piston and rings in reply to Ron in Nebr, 11-21-2005 22:07:47  
I re-read your question after I posted the first time, sounds like maybe you haven't had the rings off the pistons....anyhow:

The answer to the last part is that nothing keeps the ring gaps from lining up occasionally as they rotate. Some early engines(Hudson Hornet for example) and some motorcycle engines had the rings pinned so they couldnt rotate. But the rings on most engines rotate by design- the reason being is to keep the ring grooves from building up with carbon and causing the rings to stick.

Rings rotate enough that if the gaps do happen to line up once in a great while they don't stay lined up long, and if your rings aren't worn to the point where the gaps are too wide then it isn't enough to affect anything....which, along with the fact that rings lose tension as they age, is yet another great reason to re-ring her while she's apart.

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Rexy

11-21-2005 16:43:24




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
I would install new rings and hone the cylinders at the very least. If you need information on where to find the correct rings send me an email.
You can purchase a honing tool at most any auto parts store for around $34.00, depending on the size of your cylinder bore.



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georgia Boy

11-21-2005 16:33:06




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
Rings are cheap, relatively speaking. I don't see why you wouldn't install new rings.



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Allan in NE

11-21-2005 15:47:01




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
Jgeorge,

Guess I'm like Hal. Why did you even bother to tear it apart?

Allan



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Nebraska Cowman

11-21-2005 15:40:25




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
honing the cylinders to break the glaze is more important than new rings. if you can't afford to borrow a hone, at least run your hand in the hole with some sandpaper.



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Janicholson

11-21-2005 16:49:43




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 Re: reinstalling old piston and rings in reply to Nebraska Cowman, 11-21-2005 15:40:25  
If the rings you are using are good (end gap within spec, and strong, or low hours) go for it.
A glaze breaker (abrasive beads on the end of bristle like brush looking device) is minimal.
The crosshatch pattern of scratches should be at 35-40 degrees in the cyl. 280 silicon carbide open coat, if you paper it.
The rings may turn some, but not much, and it matters especially on used parts.
The ring clearance in the ringlands should be less than .0015" measured with a feeler gauge. If more it will be an oil user. Best of luck, it will go well if the parts are good.
JimN
JimN

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jayw

11-21-2005 15:29:04




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
If you got her apart put new rings in her she deserves it. And you wont be sorry



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El Toro

11-21-2005 15:16:44




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
I was wondering why you would dismantle the engine
and just reassemble it without doing anything?
I don't think the rings rotate, that's why we separate them when installing them on pistons. Hal



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RM

11-21-2005 15:30:46




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 Re: reinstalling old piston and rings in reply to El Toro, 11-21-2005 15:16:44  
The main concern is to make sure that you install the rings on the same piston they came off and in the same order ie. top compresion, bottom comp. then oil ring ,also you install the piston in the same cylinder it was in orginally. Follow the book on clocking the rings. Rings usaully do not rotate. The reason for reinstalling everything the way it came apart is because it has formed a wear pattern. Good Luck

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jgeorge

11-21-2005 15:34:57




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 Re: reinstalling old piston and rings in reply to RM, 11-21-2005 15:30:46  
I did this and oiled the pistons / rings. I hope they find the spot they were in before and seated.

thanks for the reply.



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Michael Soldan

11-21-2005 15:13:14




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 Re: reinstalling old piston and rings in reply to jgeorge, 11-21-2005 14:54:43  
A mechanic friend has helped me do a couple of engines and this is what he does. He takes a can of STP and dips his fingers into it and slathers the walls of the cylinder, works it around the entire surface of the cylinder ,squirts some oil onto the surfaces and then slides the piston into the sleeve or bore. The piston and rings are lubed for start up. We set the gaps of the rings at different degrees around the piston..the chances of them all lining the gap up is pretty thin. Then before starting the engine, with plugs out , we spin the engine over until oil pressure has built up, then we are ready to start the engine. Just plain oil will do to lube the cylinder..good luck ..Mike in Exeter Ontario

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