Lapping the rings ? Why take the time

[GoFast.....]

I would love to be reminded of why we do this instead of just putting them on

[Sonny S.]

same reason as hitting the ends with a file    


Edit :   I don't lap the rings.
I do however hit the cut edges with a file, and lightly slide the ring edges over a piece of oiled 600 grit to remove any burs that might be there. Then I clean the rings. I'm not in the engine building business though, pro's might do it different.

[wfolarry]

It's all in the details.

[Faast Ed]

I did not lap my rings, nor file them when I did my build last year.

Had a nice little line up my cylinder walls as a result.  LOL
Nothing deep, but enough to get my attention when I pulled the heads off for the bigger valves.
Haven't had any problems from it, but I do know what to do next time.

[tireater]

Have you got a link to the instructions...I'm feeling dumb again...

[POORBOY]

This tool is handy     http://www.box.net/shared/il9n3t5sp0

[Ken R]

I cheat. 

Buy my pistons, cylinders, and rings from Bishop's.  Hammer prepares them and inserts the pistons into the cylinders for me with one c-clip not installed.  Makes my builds quick, easy, and worry-free.   I wouldn't gap and lap enough rings in my lifetime to stay trained in my home workshop. 

Ken

[PanHeadRed]

>I would love to be reminded of why we do this instead of just putting them on<

AFAIK we don't, unless you are trying to set a NHRA world record or win the Daytona 500, IMO you are doing more harm then good if you use the ring pack provided with the piston.

AFAIK the typical piston ring groove is held to a tolerance of .0007" why would you want to thin the ring by lapping? Unless you are working with a thicker ring and trying to bring them down to min clearance?

IMO lapping a "standard" ring pack opens the tolerance up providing "potential" for gas to escape behind and through the piston groove, not to mention the "potential" to ruin the ring face contact with the cylinder (perpendicularity).

IMO - De-burring as Sonny states, is a good thing, changing the manufactured dimensions may not be in most peoples best intrest.

If lapping does not change the dimensions (thickness), IMO it's not worth the effort.

Maybe I'm in the dark about the intent of this post.

[POORBOY]

I just remove about half of the coating so ring can move free without sticking ,just something I picked up from old timer,maybe its not important but I do it anyway. Hit the edges with a stone file

[PanHeadRed]

PB, I am sure you are careful, but for the other readers, I would caution against removing any of the coating, it is on there for a reason.

[Reddog74usa]

 

[jsachs1]

Must be MAJOR "TINKERITUS". 

[wcgrinder]

Are we talking about lapping the top or bottom of the ring? If so Let me share some experience.If you are running a  shelf piston.You do not want to lap the rings as the clearance is allready to loose lapping the ring will only make it worse.
I our racing engines we will have the ring lands cut a tick undersize. Then we will lap the rings (in a special fixture) on a granite surface plate.the fixture helps insure that the ring thickness is true.During the lapping process we constantly check the clearance between the ring land and the ring.
Most shelf pistons have what is called a single pass ring land.What that is,is when the lands are cut they are done with a gang  tool and are machined to size in one operation or pass.Because any time you machine anything you will get some  tool deflection or pushoff of the tool bit there will be some imperfections in the piece being machined.The way to minimize this is to make slightly smaller first cut then a final cut or finish cut.This make for a better land that will seal much better. Most piston manufactures will do double pass ring lands upon request (all our pistons are custom made to order with double pass lands) However C.P and Mahle do it on all there pistons custom or shelf.
We allways use file gap rings.Put the rings in a ring gauge and check the circumference for light passing between the ring and the gauge. "D" rings are quite common. CAREFULLY deburr the ends and clean with lacquer thinner. 
If you are having problems with rings fitting in a shelf piston I would suggest changing pistons or rings           

[Don D]

Very informative, I knew the concept but the terms threw me single pass, double pass. Thanks very much for that
In my stock class racing days the off the shelf pistons had terrible ring back clearance and there was power to be had by shimming behind, Sealed Power made the shim stock.

[GoFast.....]

With a name like wcgrinder you otta know

[POORBOY]

Then we will lap the rings (in a special fixture) on a granite surface plate.the fixture helps insure that the ring thickness is true

So do I

[wcgrinder]

I could Tell ya what "wcgrinder" means but then I would have to--- well you know>

[Don D]

And the plating
No plating at all, no buildup, it is either iron, zinc, or mag phosphate, a conversion process same as used on flat tappet cam lobes.