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MONTAC Enterprises
ATTN: MTB Madness
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Azle, TX 76020



Anal Retentive's Guide to File-to-Fit Piston Rings


Part of the build-up for my new engine necessitates filing the Total Seal TS1 Rings to fit the cylinder bores properly.  It occurred to me that some folks may not have ever done this, and that it might be a good idea to put together a "How-To" guide on ring filing.   Now, as anyone who knows me will tell you, I am somewhat particular about how I do certain things.... well everything actually.  So, this article illustrates the method "I" used to fit my piston rings.

Note:  Click on any image to pop up a larger version.  If your browser "auto-resizes" it, you can hover your mouse cursor over the picture to bring up the "size-toggle" button in the lower right-hand corner of the image.  Click on that button to see the image full size.


Click for larger version...Here are the basic tools and materials I used:  manual crank ring filer clamped to table with a 12' clamp, 320 grit wet-dry paper on a sanding block, flat diamond file, feeler gauge set, ring squaring tool, and of course the Total Seal documentation for the TS1 Gapless Second Ring set.

I bought both the ring filer and the squaring tool from a Total Seal dealer here locally.  If you don't have these tools, get them.  They are not optional.  You can't do a proper file-to-fit job without them.

Click for larger image...Beginning with the top compression ring, refer to the documentation and you'll find where it says to install the ring with the bevel located on the inner diameter FACE UP.  Thus you should file the rings the same way, with the bevel UP.
Click for larger version...Next thing I do is to install the raw ring in the bore to get a quick pre-measurement to see where I am at.  You should install the ring oriented to the cylinder just how it will be installed on the piston.  In this case, the ring is 180 degrees reversed from where it should be,  but I'm just getting a quick reference for starting purposes.


Note: it should go without saying, but you MUST install the ring in the cylinder bore into which you will install the ring during final installation.  The way I do it is to take all the rings out of the box and make up individual cylinder "ring sets".  Then I place each ring set in its own Ziplock bag, and label it with the corresponding cylinder number.  AND I NEVER have more than ONE bag open at a time.

Click for larger image...Use the ring squaring tool to square the ring in the cylinder bore.  This tool pushes the ring down in the hole about 1".  Note:  When you order the tool, be sure to get the largest diameter one that will still fit inside the bore.  In this case, the tool is designed for piston bores with a size range of 3.810"-3.900" and is Total Seal Part# 8900.
Click for larger version...Holding the tool flat against the block deck, use your fingers to double check that the ring is flush against the face of the squaring tool all the way around.
Click for larger image...Use the feeler tool, measure your starting place. Note in the image, that the blade is NOT flush against the wall of the cylinder bore.  This is a BAD measurement.  The blade enters the gap, but won't fully seat.  This indicates gap faces that are not square.
Click for larger version...A couple of revolutions on the ring filer confirms that the faces are NOT true.  Note in the image the shiny portion of the gap face.

You should file BOTH faces just until the face is flat (equally shiny across the entire face).  Don't get carried away and file too much.  You don't want to open the gap too wide.

Click for larger image...Place the ring on the filer with the wheel in the center of the gap, and the inside ring faces touching the posts on either side of the wheel...
Click for larger version...Now, keeping the ring against the posts, rotate it until the gap face contacts the abrasive wheel.  Hold the ring down tightly with your finger et al. device.  Then begin filing by turning the handle/wheel AWAY from you.  This is so the filing motion is toward the INSIDE of the ring.  This is very important.  The abrasive wheel will leave a sharp bur on the exit side.  If this bur is on the bore face, it may scratch the bore, and it will at minimum hold the ring away from the cylinder wall.

File a little bit off the gap face...

Click for larger image...Insert the ring into the bore with the squaring tool as described above.  use the feeler gauge to determine the "good" starting gap measurement.

The standard I use for what is a "GO" and "NO GO" on the feeler gauge is:

A "GO" is when the feeler gauge will drop vertically through the gap under its own weight.

A "NO GO" is of course when it will NOT slip down under its own weight.

Here we have a "GO" measurement, as the feeler gauge dropped into the gap under its own weight and is resting on the block deck.

Also note that the blade is flush against the cylinder wall.

Click for larger version...Here is the starting measurement for this ring on this cylinder.  I do this so I will know approximately how much material needs to be removed.

Now, remove the ring CAREFULLY from the bore, and begin filing it a little at a time. Reinsert into the bore, square it up and re-measure.

Repeat this procedure until you achieve the required ring gap for that specific ring for your application.  As you do it more, you'll get a "feel" for how much material to take off.  But it's better to file material off VERY gradually to make sure you don't overshoot the required gap.

You can ALWAYS take more material off, but it's impossible to put it back!

Lather, Rinse, Repeat...

Click for larger image...I've repeated the file, install, measure procedure about 6 times, and have the gap exactly where I want it...
Click for larger version...For this ring and my application, the gap is 0.022".

Total Seal includes a table/formula in its documentation to assist you in determining an APPROXIMATE ring gap.  However, certain factors in your application may/will require you to increase or decrease the gap size.  in my case, I have widened the suggested gap by a few thousandths of an inch due to it being a turbocharged engine AND because the block is filled.

Click for larger image...Just so you can see an example, here is a picture of the feeler gauge set at 0.023" on the ring above.  Note that although the feeler gauge went into the gap fairly easily, it would NOT drop through the gap under its own weight.

Also, note that I have the ring gap oriented as it will be installed.

Click for larger version...I have the right gap size now, but I am not finished with this ring.  Filing the ring causes burs around the edges of the gap face.  These burs will reduce the side and back clearances for the ring to piston.  They will also chew an aluminum piston ring groove to pieces.  You have to take these burs off completely.
Click for larger image...I use a combination of this diamond flat file and a sanding block with 320 grit wet/dry sandpaper or finer.  File/sand the burs off being careful not to remove more material than absolutely necessary.
Click for larger version...Here is the machined gapless second compression ring just after I have done the initial facing procedure.  Note the bevel on the inside face, and the step machined into the outside face to accept the rail.  This ring is currently UPSIDE DOWN.  It installs into the bore with the bevel and step facing down.

The filing procedure for the gapless second ring is essentially the same as the top compression ring except that you have to file the rail too.

I file them separately since the rail tends to slide back into the groove when done at the same time.

Note: the rail when installed on the machined ring is slightly undersized in diameter.  This is normal.  It expands when in use to seal against the cylinder bore. Thus it is not necessary to cut the gap in the rail quite as large as the one used on the machined ring.

The oil ring rails are done the same exact way as the top ring, though mine were above the minimum required out of the box.

Well, that's it... That should give you a good start, and a good idea as to the detail I go into to insure that nothing is overlooked.  In my opinion, you can never be TOO anal retentive when building up a high horsepower engine.

Have fun, and be safe!



Copyright (C)2003 MONTAC Enterprises.  All Rights Reserved©
Revised: March 03, 2006 .