Oversize ring in a standard bore

Cas · Mar 4, 2015

There is a post below about rings. Last few years, I have talked to a few cracker jack engine guys. Some of them can measure to the 0.0001. If the guy has a gas(not diesel) engine they are putting in over size rings in and grinding off enough material for a good ring gap.
Naturally the ridge in top of the block is taken off. Also, the piston can not have so much wear that it will slap. Cylinders are ball honed with a coarse grit ball hone(can not remember the grit),
This would be for engines where not a lot of hours are put on the machine.
I did this once on my old Case 530 backhoe. It was about 4 years ago and the engine has a little over 450 hours on it now and no problems. Would any of you guys do this on a lower value machine? Forgot, put bearings in it they are cheap and I ground the valves,knurled the guides, used Chevy umbrella valve seals, and lapped the valves.

mite-help · Mar 4, 2015

sure. you can file the ring end gaps on oversize rings to fit the cylinder. 'engine blueprinting' this works on new perfect bore. but think about 'removing the ridge' the amount of that ridge tells you how much cylinder wall is forever gone, mostly in combustion area, the result is a nice funnel shape. no way to make gap work out at both ends of travel if well worn.

Den N Ms · Mar 4, 2015

Cas,Yes it can be done if the cylinder bore is not tapered to much if it has to much taper it will cause the ring lands to wear quickly and loose the compression seal.If they are not tapered to bad,check and set the ring gap at the bottem of the ring travel in the bore to the minimum ring gap clearance. You can also knurl the piston skirts if needed.It will work well on a low use engine.

Steve@Advance · Mar 4, 2015

Yes, it can be done, not anything difficult, just time consuming. Will you gain anything? Probably not much. Going back together with honed cylinders and used pistons will buy some time, not considered a true rebuild. You'd be better off to go back with iron rings. They're soft and conform to less than perfect cylinder walls and worn ring lands better than moly or chrome, if you can get them.

Filing the end gaps is more for performance engines, or an engine that won't see any break in time, built right and run full power from the start up. And it would increase the ring life somewhat if you were going for long term endurance.

bison · Mar 4, 2015

If you're concerned about loosing compression you can also install gap less rings

BushogPapa · Mar 4, 2015

Just "Lapping the valves" is YOU fooling yourself..

That won't amount to much when carbon builds on that 1/4" wide seat..!

You will be surprised just how small the end-gap will be with the proper rings for that Bore-size..

Yes, the ridge MUST be eliminated or the top ring will never seat well and you are risking problems with out-of-round and tapered cylinder walls.

Remember, there is Ring Wear at the bottom of the cylinder also...

Rings can be worn so bad you have nearly 1/2" end-gap and new rings will close that up fine for many hours of use (Gas engine).

al71 · Mar 4, 2015

Watch and fit the ring gaps very carefully and listen to the experienced men on this forum. Al71

John M · Mar 4, 2015

Not buying it!

cole in mo. · Mar 4, 2015

Oversize rings, even filed for a proper ring end gap, will be stiffer than the right ones. This puts more pressure on the cyl walls, causing more and faster wear. Also they tend not to break in like they should, and cause more drag.

Mel in SW Iowa · Mar 4, 2015

If your engine measures out with little to no cylinder taper, hone marks still prominent in the cylinders, pistons still at least in spec, but rings with excessive gap, by all means re-ring one. But if new standard rings for the bore aren't pretty close on ring gap, you probably didn't measure correctly. See Cole in MO. BTDT When you install rings in a funnel, they will never seat properly. Gapless rings might work for a while, but I expect they will wear out quickly. Hope is not a good measurement for engine assembly. Good luck, Mel

skip33652 · Mar 4, 2015

its all about the math when file fitting rings you must allow clearance in tight part of the cylinder wall . this is so that if ring heats up and expands it does not stick in the bore . minimum clearance is about.0045" per inch of bore or about .020 on a 4" bore . now if the cylinders have .010 taper to them your ring end gap will be about .050" at the top of the bore where the most leakage will occur if the bore is wore .015" the ring gap will be about .070" .kinda hard to keep the air on the top side of the piston .

If one uses gapless or two rings instead of one you might get by longer but that ring is going to act like a piece of wire that got bent one too many times eventually.Paul

Bob · Mar 4, 2015

"Oversize rings, even filed for a proper ring end gap, will be stiffer than the right ones."

Huh???????

Bob · Mar 4, 2015

As the others have said, the bore wears more at the upper area of ring travel than at the bottom (which typically doesn't wear much at all).

So no matter how much it seems OS rings will be a good deal in the upper area of the bore they ain't gonna squash together enough not to create a disaster at the lower area of ring travel.
Ring fitting tips

Oversize ring in a standard bore

Cas

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mite-help

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Den N Ms

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Steve@Advance

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bison

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BushogPapa

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al71

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John M

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cole in mo.

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Mel in SW Iowa

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skip33652

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Bob

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Bob

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