Piston Ring Grooves

[thompson1600]

I have a couple pistons that appear to still be useable, not scored up and the bottom of the apron shows little wear. However, the rings fit tightly in the grooves and don't have good flex movement to compress and release. I've cleaned the grooves out, but was wondering if there was a way to "open" up the grooves so that the rings can move freely.

Thanks

Tom

 

[Al Smith]

Were the pistons oxidized?I salvaged a McCulloch piston by using,believe it or not,a thin fingernail file to clean up the top ring groove .Another option is to lap the rings.To do so,use a lapping plate,or a smooth ground piece of steel,and fine lapping compound.Use a figure 8 pattern during the lapping process,and clean all the compound off the rings before installing.

 

[Al Smith]

An after thought! Do a "google" search on making piston rings.There are several good articles on the subject,which go in detail about the lapping proceedure.

 

[eric_271]

If you havent done it yet run the end of the ring all the way around the ringlan and look for a tight spot. If its just a tight spot you will make things worse lapping the ring. Get a magnifying glass and inspect the groove real well.

 

[Molecule]

sometimes it's not the width of the groove itself that binds the ring, but just a smidgen of smudge that has compacted into the two interior corners (upper and lower interior corners) of the groove, causing the back edge of the ring to bind. before taking xtra fine grit sandpaper to the sides of the groove (e.g. tops and bottoms of the groove to "widen" it), try running a dental pick (ask your dentist--he may have some old ones no longer suitable for his 'a-picking which he will give away) or exacto knife/razor blade around the corners, to just clean out the tiny filet of grunge which gets compacted in there

 

[thompson1600]

I have tried a pick and cleaned them out. It does seem like it has a tight spot or area. I tried sandpaper in the groove, but that was too general and seemed like I would round over the edge. I will try a fingernail file. Any other ideas or suggestions?

Thanks

Tom

 

[Lobo]

Tom if its just a tight spot from baked on dirt go and purchase a piece of mesh sanding screen used by dry wall installers (not the dry wall sanding paper but the sanding screen) it is a real mesh screen with tiny holes in it and every part of the screen is impregnated, every part of it is usable. you can rip it in to strips and fold a crease in it to easily get in to the piston grooves.

 

[ErrolC]

if you want to get the piston real clean (as new) leave the piston crown upside down soaking in paint stripper in a small jar over night..purchase a soft brass wire brush (toothbrush sized) from the local hardware store and it will brush out like custard. Tergo stripper is what I use..removes most oxide & rust as well.

 

[Cut4fun]

Have you tried a ridge reamer. Comes in several different sizes, usally 4 sizes per set.