another ring question

have you guys ever used next bore size rings and just filed the end gaps so they correctly fit? ( ie, 4th bore rings in a 2nd bore hole) It's been done on car engines and aircraft piston engines as well.

I just want clarification on this because I have a spare set of 4th overbore rings that I listed on ebay with the description saying that they are good up to the 4th bore - meaning you can use them on smaller bores by just checking and filing the ring gap for the smaller bore size.

I'm getting some questions on it and it seems no one has ever heard of this or done this before

Doesn't work. The ring is only actually round when it is in the correct bore size.

jzanutto wrote:

have you guys ever used next bore size rings and just filed the end gaps so they correctly fit? ( ie, 4th bore rings in a 2nd bore hole) It's been done on car engines and aircraft piston engines as well.

I just want clarification on this because I have a spare set of 4th overbore rings that I listed on ebay with the description saying that they are good up to the 4th bore - meaning you can use them on smaller bores by just checking and filing the ring gap for the smaller bore size.

I'm getting some questions on it and it seems no one has ever heard of this or done this before

Yes, it is an old racing trick. Most of the time the next oversize ring is used. You can custom set the end gap, if thats your thing. The theory was to have a stronger, ring pessure, forcing the ring agaist the cylinder wall, therefore creating a better seal.

Most of the time when you go to rebuild one of these motors, the cylinder walls are shot. In my opinion, they take longer to break in. Simply put, not worth my extra time to do it. Now days, most piston kits come with the ring end gap, real close to what you need. I just never saw the guys who did it, go any faster, then the next guy.

Both of the previous posters are correct. The larger ring can be made to fit the smaller bore, but it will not have an "optimal" seat and may cause some problems with oil consumption or blow by, agian I saw this in race applications where minor oil consumption is tolerated. In a pinch you could put an engine together that way, but if you are planning things out put the correct size rings in.

nope,it wont stay round with that much differance from designed bore

jzanutto wrote:

have you guys ever used next bore size rings and just filed the end gaps so they correctly fit? ( ie, 4th bore rings in a 2nd bore hole) It's been done on car engines and aircraft piston engines as well.

I just want clarification on this because I have a spare set of 4th overbore rings that I listed on ebay with the description saying that they are good up to the 4th bore - meaning you can use them on smaller bores by just checking and filing the ring gap for the smaller bore size.

I'm getting some questions on it and it seems no one has ever heard of this or done this before

We used to do it with car engines back in the stone age. The rings are only perfectly round at the design value diameter.... but, they come in sizes that are +.25 mm (.010") increments. BTW, a worn cylinder isn't round anyway. The cylinder walls don't wear evenly.

If the cylinder has wear, a new set of stock rings won't fit the bore right either, (they will over expand). If the bore wear is approaching .005", a set of +0.25mm rings will probably work but I would definitely hone the cylinder walls good. Rings are made of much harder steel than the cylinder and the edges are sharp. They will "cut in" the cylinder somewhat and seal in if broken in well and the cylinder is close to round.

With cars, a "hone and ring" was usually done to get another 20k or 30k miles before a rebuild. It's not great, and you should only go to the next size up in diameter.