Piston Ring Locator

My first homemade tool post!

As a side job, I rebuild engines for a local golf cart business. I generally see the same types of engines over and over, so making a tool to help speed things up is a benefit.

When I build the engines, I always check the piston ring end gaps to make sure they aren't too tight. I have found some that are and would have been catastrophic had I installed them. Anyway, I have to push the ring down into the bore to a specified depth and measure the gap with feeler gages. Normally, I use a new piston held upside down to square the ring in the bore, but it's not exactly accurate and it is somewhat cumbersome.

So I whipped up this little tool from a used piston to make it easier. The length between the top and bottom of the tool is within .003" all the way around, so much more accurate.

As I get in other engine types for rebuild, I will make the same tool for each.


Attachment 33081Attachment 33082Attachment 33083Attachment 33084

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Thanks Rikk! We've added your Piston Ring Locator to our Piston category,
as well as to your builder page: Rikk's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-piston-ring-locator"> <img src="/uploads/229050/homemade-piston-ring-locator.jpeg"/> </a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/homemade-piston-ring-locator">Piston Ring Locator</a> <span> by <a href="https://www.homemadetools.net/builder/Rikk">Rikk</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/piston-ring'>piston ring</a>, <a href='https://www.homemadetools.net/tag/measurement'>measurement</a> </div> </div> </div> </div>
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Needs a little explanation? I’m presuming that you milled the bottom of the piston square to the top & now you are just pushing the rings down the cylinder equidistant & then measuring the gap after the piston is removed?

Rikk,

The best ideas are usually the simplest. Great idea fully explained.

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Originally Posted by Wildwilly

Needs a little explanation? I’m presuming that you milled the bottom of the piston square to the top & now you are just pushing the rings down the cylinder equidistant & then measuring the gap after the piston is removed?

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Yes sir that is it exactly!

I'm sorry, I guess I should have explained, I was just thinking that anyone who knows how to rebuild an engine, would understand. I've attached an image to help explain. I thought I had taken a photo of the ring in the cylinder, but I didn't.

Why this tool is useful:
To measure the end gap of a piston ring, the manufacturer will generally specify a depth into the cylinder that the ring must be placed. In this case 1" from the top.

The usual way of doing it, in lieu of a special tool, is to turn the piston upside down and use the crown of the piston to square up the ring. I would just put a couple marks with a sharpie around the piston to establish the correct depth. The cylindricity of the piston gets the ring somewhat square to the bore, but because there is a lack of a positive stop, the piston can still rock a little in the bore and leave the ring cocked. With this tool, the ring is quite square in the bore, thus giving me a more accurate measurement of the ring end gap.

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Originally Posted by tonyfoale

Rikk,

The best ideas are usually the simplest. Great idea fully explained.

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Thank you Tony!! Coming from you, that means A LOT.

I've secretly followed you here for some time, your work on bikes is amazing. I've been into old bikes my entire life and gave AHRMA a try years ago on a friends CB350.
Thanks again!

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When I build the engines, I always check the piston ring end gaps to make sure they aren't too tight.

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It's nice to hear that you check the ring's end gap. I've seen several engines where that wasn't done and then the "mechanic" wonders why there's a problem w/the engine. In fact I once had a mechanic tell me that it wasn't necessary to check the end gap on new rings as they were manufactured to fit w/out having to check them. This was by a mechanic that worked at a authorized Ford engine rebuilder.

Quote:

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Originally Posted by Rikk

Thank you Tony!! ..... your work on bikes is amazing. I've been into old bikes my entire life and gave AHRMA a try years ago on a friends CB350.
Thanks again!

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After a long layoff from racing I started again and for a couple of years it was with AHRMA but then I came to live in NH in the US for a while and then did most of my racing with the USCRA at Loudon. Insurance got impossible and so in the future I'll be racing here in Spain and other euro countries.

My comeback ride was at Daytona in 2006, I was only 62 then.

Attachment 33109 Attachment 33110 Click images for full size.

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Originally Posted by katy

It's nice to hear that you check the ring's end gap. I've seen several engines where that wasn't done and then the "mechanic" wonders why there's a problem w/the engine. In fact I once had a mechanic tell me that it wasn't necessary to check the end gap on new rings as they were manufactured to fit w/out having to check them. This was by a mechanic that worked at a authorized Ford engine rebuilder.

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Thank you!

I've been turning wrenches since I was a boy, 49 now, when I was young, my uncles showed me a lot (lost my father when I was little) and when I didn't know how to do something, I bought a manual or found one at the library and actually read it, not just referred to it. I needed the help to learn. My thought then and now is, if there is a spec in the book for something, then it should be verified and made correct.

I have spent my life as a tool room machinist and manufacturing engineer, I understand that things sometimes make it thorough inspection and might need some tweaking.

These are just golf carts, but my and my friends business names are on it. Everything gets the same level of attention to detail, be it a golf cart or one of my son's dirt kart racing engines. To me, it provides a mental satisfaction to know I have made it as close to perfect as I can.

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Originally Posted by tonyfoale

After a long layoff from racing I started again and for a couple of years it was with AHRMA but then I came to live in NH in the US for a while and then did most of my racing with the USCRA at Loudon. Insurance got impossible and so in the future I'll be racing here in Spain and other euro countries.

My comeback ride was at Daytona in 2006, I was only 62 then.

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62? Just a pup in racing years. :) As long as you can crouch and lean, you can still ride.

I originally did some laps on my friends bike in a parking lot and loved it. He knows I've ridden my entire life and told me if I got my racing license he would let me campaign his bike for a day. So I did and loved it. When time and life permit, I would love to build a bike to run now and again.

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Originally Posted by Rikk

My first homemade tool post!

So I whipped up this little tool from a used piston to make it easier. The length between the top and bottom of the tool is within .003" all the way around, so much more accurate.
As I get in other engine types for rebuild, I will make the same tool for each.

Attachment 33082

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Very good idea. I believe you could solve the .003 OOS issue easily.
The process of manufacturing washers [punching ID, stamping OD] does not insure flat parts. Next, surface of cast piston is likely not dead perpendicular to skirt, especially in 3 locations. Finally, small relative area of cap screw could 'dent' each washer into different cup shapes.

Use 3 smaller, narrower [there fore stiffer] contacts held the same way. 3/16" keystock, dowel pins, etc. 3 points of contact is always stable, yet no assurance each is on same plane.
Just like surveyor's tripod, adjustable legs AND leveling jackscrews.

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Originally Posted by Toolmaker51

Very good idea. I believe you could solve the .003 OOS issue easily.
The process of manufacturing washers [punching ID, stamping OD] does not insure flat parts. Next, surface of cast piston is likely not dead perpendicular to skirt, especially in 3 locations. Finally, small relative area of cap screw could 'dent' each washer into different cup shapes.

Use 3 smaller, narrower [there fore stiffer] contacts held the same way. 3/16" keystock, dowel pins, etc. 3 points of contact is always stable, yet no assurance each is on same plane.
Just like surveyor's tripod, adjustable legs AND leveling jackscrews.

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Agreed anything can be refined but a.003 thou error is acceptable for this application and is better than using a sloppy unringed piston to square a ring in a bore, you will be relying on touch with a feeler gauge for the final measurement. Most of my work is one offs otherwise I would copy this idea.

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Originally Posted by olderdan

Agreed anything can be refined but a.003 thou error is acceptable for this application and is better than using a sloppy unringed piston to square a ring in a bore, you will be relying on touch with a feeler gauge for the final measurement. Most of my work is one offs otherwise I would copy this idea.

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True, in this application I have an .008-.016 tolerance, so a few thou tilt won't change things much. Normally file for .008, recheck then hone the corners and check again. Generally end up with .009-.010 in the end.

The bores in these things are surprisingly resilient. First thing to go is the overhead rockers/cam. Always because of dirty oil plugging the oil system. People think these things will run forever without changing the oil.

Quote:

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Originally Posted by Rikk

62? Just a pup in racing years. :) As long as you can crouch and lean, you can still ride.

I originally did some laps on my friends bike in a parking lot and loved it. He knows I've ridden my entire life and told me if I got my racing license he would let me campaign his bike for a day. So I did and loved it. When time and life permit, I would love to build a bike to run now and again.

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Unfortunately, I am not 62 anymore.
Be careful if you try racing again, it is highly additive and takes over.

I'm not familiar with small industrial type motors, and my visualizations tend to minimize deviations. .003 on a small bore is not very consequential; it will alter measurable gap as bore increases. So the easier technique might felt tip a particular point to index the gap each time. Then angled or not, moving to file, replacing to check would create least possible variation.

Quote:

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Originally Posted by olderdan

Agreed anything can be refined but a.003 thou error is acceptable for this application and is better than using a sloppy unringed piston to square a ring in a bore, you will be relying on touch with a feeler gauge for the final measurement. Most of my work is one offs otherwise I would copy this idea.

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I am amazed that there seems concern over a 0.003" error. As Alan says that is acceptable. It is a very simple calculation that over a bore diameter range of 50 to 100 mm that error represents an off square error range of 0.086 to 0.043 degrees, which is totally inconsequential. The difference in the ring gap would not be measurable with garage feeler gauges.

Another who had dalliance with road racing, last century...

I was taught by my father, a garage owner, that best practice
was always to measure the ring gap in the unworn portion of
the bore, namely below where the rings ran, the gap would
always be smallest there.

Quote:

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Originally Posted by Rikk

Thank you!
I've been turning wrenches since I was a boy,...<<<snip>>>
These are just golf carts, but my and my friends business names are on it. Everything gets the same level of attention to detail, be it a golf cart or one of my son's dirt kart racing engines. To me, it provides a mental satisfaction to know I have made it as close to perfect as I can.

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I think exactly the same way; by way of the things we used to buy had one man's or assembled men's names very closely associated with those products. That slid downhill a long way as trend toward made up words came about. "Rebranding they say", no it's DE-branding. "It more closely aligns with our customer base", hah, what of those who fueled the success? Pick one, them or new ones who can't spell or write full sentences?

Quote:

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Originally Posted by Isambard

I was taught by my father, a garage owner, that best practice
was always to measure the ring gap in the unworn portion of
the bore, namely below where the rings ran, the gap would
always be smallest there.

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It simply makes no sense to set the ring gap in the part of the stroke that does not see the rings.

I can see this will make the job quicker. Good stuff. Thanks. Mr Mikey.

Quote:

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Originally Posted by mr mikey

I can see this will make the job quicker. Good stuff. Thanks. Mr Mikey.

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Thank you, it does for sure. Two piston rings and two oil scraper rings for each of two cylinders. Probably saves me ~10 minutes or so. Less tedious that's for sure.