heptadecagonal hone job - Howdy Doo-it ?

[Dan Timberlake]

.010" O/S LS something or other. 4.016"Ø +/-.
Details of what actual hone was used to create the O/S bores are unknown.

The regular vertical "stripes" sort of line up with the piston's oil ring drain holes.
I've seen 1000 CC iron cylinder Harley sportsters wear with stripes like that at the head bolts when the finished without torque plates. On those the bore gage picked right up on the ~.0003" bumps/tight spots as .0005" smaller diameter.

On this LS there are no tight spots noticeable with a bore gage, but we weren't looking very hard for it at the time either.
I suggested a "light test" to check if the nitrided 1.2 mm steel RING had distortion issues, NEVER expecting the cylinder was anything other than fairly round. The gap between ring and cylinder is less than .0015" but might be a lot less. We are working on quantifying that.

This cylinder reportedly had excessive blow-by.
Other cylinders have very similar but fainter "striping" but the ring blocks all light.

The owner is keen to understand how a hone could possibly create such a non-round "cylinder" shape.

Does anybody know how to make a Sunnen CK-3000 Standard Hone Head ( or any rigid honing setup) create such a wacky cylinder shape ?

cylinder stripes 23 crop .jpg

20210810_194016 - 25.jpg

20210810_193905 25.jpg

[hoodeng]

Do the number of waves match the number of stones on the CK3000 head? or a division of?

Cheers.

[BillK]

I dont see how the hone would possibly do that in such a perfectly vertical pattern. I would be more inclined to think that the oil ring itself caused the problem. Maybe the wrong expander ?

[David Redszus]

I would send those pix to MAHLE Motorsport and ask for their opinion.

[shoedoos]

OP, any updates on this mystery?

[In-Tech]

Rings wadding up from end gap problem.

[cgarb]

Lucky the tops stayed on the pistons then.

[mxer]

Chatter of hone head while honing. Frequently caused by stones not trued in and or to fast RPM usually

[mxer]

Also issue can be worn Hone head also

[modok]

How does it happen? just like a rotary engine gyrates, just how a Reuleaux Triangle rolls, like a gear-rotor oil pump works. How the knerl marks magically line up when you are knerling a shaft.
There is no axle, no center of rotation on a hone head.
IMO ....how does it NOT happen more often?

I think this is because the typical ORDERS of distortion of both a used cylinder or a freshly bored cylinder tend to be a low enough even number that the typical hone head which has two stones across from eachother, (or almost across from eachother) never begins doing it.
And speaking of that, if you CAN measure it with a bore gauge, then... must be an even number, and that MOST LIKELY corresponds with exactly how the stones are positioned on the ck3000, one of them offset slightly.
And if you CAN't measure it with a bore gauge, then it must be an odd number, so it was done with a hone head with the stones 180 apart. Or a ck3000 hone head improperly shimmed so the stones were 180 apart.

But it ALMOST never happens.
Some cylinders have FIVE bolts, and that could get into danger territory.....but the top of the cylinder where the distortion was, is the part that wore out...so you just can't lose.

If a typical twist drill bit produces a round hole I think it's a miracle, and you will know what I mean if you drill a lot of holes. Triangular lobe shape is the most common, but you can produce almost any odd shape, literally.

If cylinders wore INTO a triangular shape then you would need a triangular pattern hone head to make it round again, but they always wear oval, or clover shape so we use the hone head we use and never see a problem ....but apparently not 100% always.
I would like to know if it was bored and honed, or just honed to the next size? Then you could see if the blame is with the engine wore or with how the boring machine bores.

[modok]

The way to make it do that, is hone a hole shaped such that when one stone (or opposite shoe) is on a high spot, the other stone is in a low spot.

The way to fix it.... is change how the guide shoes are shimmed, (put more shims on one side and less on the other) until both stones are sitting on the high spots at the same time or at least more than halfway towards that condition.

For a cross shaped hone head two stones and two shoes.
for other situations....I have to think about it.

Or not think about it and just grab triangle shaped hone. OLD sunnen tended to have both types in basically every size.

If one starts gyrating you just switch to the other type and it fixes itself.

the odd number distortion is more dangerous because you won't see it with a typical bore gauge, may not know until the thing doesn't fit in the hole.

[modok]

That was very hard to explain, but now that I've done it it seems simple.
Perhaps the areas of my brain which handle geometry do not often interact with the part that does language?
I faintly smell fudge all of a sudden, but there is none present.

[englertracing]

How does it happen? just like a rotary engine gyrates, just how a Reuleaux Triangle rolls, like a gear-rotor oil pump works. How the knerl marks magically line up when you are knerling a shaft.
There is no axle, no center of rotation on a hone head.
IMO ....how does it NOT happen more often?

I think this is because the typical ORDERS of distortion of both a used cylinder or a freshly bored cylinder tend to be a low enough even number that the typical hone head which has two stones across from eachother, (or almost across from eachother) never begins doing it.
And speaking of that, if you CAN measure it with a bore gauge, then... must be an even number, and that MOST LIKELY corresponds with exactly how the stones are positioned on the ck3000, one of them offset slightly.
And if you CAN't measure it with a bore gauge, then it must be an odd number, so it was done with a hone head with the stones 180 apart. Or a ck3000 hone head improperly shimmed so the stones were 180 apart.

But it ALMOST never happens.
Some cylinders have FIVE bolts, and that could get into danger territory.....but the top of the cylinder where the distortion was, is the part that wore out...so you just can't lose.

If a typical twist drill bit produces a round hole I think it's a miracle, and you will know what I mean if you drill a lot of holes. Triangular lobe shape is the most common, but you can produce almost any odd shape, literally.

If cylinders wore INTO a triangular shape then you would need a triangular pattern hone head to make it round again, but they always wear oval, or clover shape so we use the hone head we use and never see a problem ....but apparently not 100% always.
I would like to know if it was bored and honed, or just honed to the next size? Then you could see if the blame is with the engine wore or with how the boring machine bores.

[BILL-C]

If you look closely you can easily see where the top ring stops at top of travel. There is no funny pattern at top of ring travel. The odd wear pattern doesn't start until the location of the oil rings. If there was a surface texture issue wouldn't the top rings also highlight it? Never once in 40 years of building and freshening race engines have i seen a sunnen hone produce such a finish. i think the oil rings are the cause of the shiny stripes.

[piston guy]

I agree with Bill and some of the others , this is an oil ring wear issue. I have seen it on one particular brand of oil ring in their "standard tension" 3/16ths oil rings. never seen it with a 3MM oil ring.