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-   94-98 2nd Gen. 12V (http://www.competitiondiesel.com/forums/forumdisplay.php?f=87)
-   -   Eyebrow cylinder (http://www.competitiondiesel.com/forums/showthread.php?t=198210)

WAYNES WORLD 10-30-2017 12:41 AM

Eyebrow cylinder
 
1 Attachment(s)
Guys,

Has anyone ever heard of a "eyebrow" cylinder finish, see photo?
The machine shop said it was no problem--------

WAYNES WORLD

biggy238 10-30-2017 12:10 PM

Take it with a grain of salt, but I've never seen it, and couldn't find it online when I searched. I'm not even certain how that would happen

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Snedge 10-30-2017 12:27 PM

I never heard the term either, but it looks like the cylinders were honed, not bored. That's maybe as far as they wanted to go with the hone to stay in spec.

Mark Nixon 10-30-2017 12:32 PM

IMO, that should have been bored, rather than just "cleaned up".
The "eyebrow" is the result of trying to offset hone out the deepest wear, hoping you'll catch the shallowest side while doing it.

Machinists try this on V-8s a lot, with similar results.

Mark.

blackmega3500 10-30-2017 12:36 PM

Quote:

Originally Posted by Mark Nixon (Post 2641987)
IMO, that should have been bored, rather than just "cleaned up".
The "eyebrow" is the result of trying to offset hone out the deepest wear, hoping you'll catch the shallowest side while doing it.

Machinists try this on V-8s a lot, with similar results.

Mark.

The ONLY "Google image" I saw from searching on intrigue was....

Engine Porting

WAYNES WORLD 10-31-2017 01:05 AM

Eyebrow cylinder
 
2 Attachment(s)
biggy238,

Thanks for the effort------

Snedge,

I'm leaning your way. They may have had the pistons before the machine work was started.

Mark Nixon,

I'm wondering if they rushed the job or trying to keep in spec? My concern, is it OK? It sounds like this has been done before. What is the result? Is it still able to work well?

blackmega3500,

Good but how will this effect my engine is my concern?

Thanks for the info Guys-----

WAYNES WORLD

badbowtie 10-31-2017 04:45 AM

I wouldn't be happy if it was mine. Mark said it is from offset honing the cylinders, save a buck or do it right. I would want it bored with larger piston and have it true center. It can't be good for high performance or long life either one. I also don't think I would continue to use that shop , if they didn't discuss this with you.

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biggy238 10-31-2017 06:36 AM

Offset Boring Cylinders - Yellow Bullet Forums

Free Power! offset cylinders explained | RideApart

I may be misunderstanding, but the only way to get that pattern is partial contact of a hone? (offset as Mark called it)

Most of what I found this morning is moving the cylinder. Honing it would create an elipse.

I would run it just to see what happened.

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jasonc 10-31-2017 07:57 AM

It's how the cylinder was worn and the hone couldn't make it to the low spot, can you feel the depression with your finger. It's not ideal but I bet will run fine.

Smokem 10-31-2017 09:33 AM

It was clearly offset honed, my concern with this instance is that it appears the top and possibly second compression ring will pass the depression while reaching TDC.

biggy238 10-31-2017 10:57 AM

Clearly....

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WAYNES WORLD 10-31-2017 12:08 PM

jasonc,

I can slightly feel the spot.

Smokem,

The shop said it would be OK. I'm concerned but we'll see what happens-------

Thanks, WAYNES WORLD

WAYNES WORLD 10-31-2017 12:20 PM

Eyebrow cylinder
 
1 Attachment(s)
Guys,

A close up------

WAYNES WORLD

WAYNES WORLD 11-02-2017 12:09 PM

Eyebrow cylinder
 
Guys,

I talked to the machine shop about this---------

This is their reply------

Good to talk to you today, as we discussed the eyebrow is not a issues in this application because the cylinder is going to distort in use, the only way to fix this would be to hone the block until it is gone and then it would have excessive clearance and the rings would not seat well in that case or bore the cylinder bigger and put oversize pistons in it, the downside to that is the cylinder wall will be thinner and this engine has a problem with breaking cylinder anyway, so this is the lesser of all the evils is leave the eyebrow there, we have seen this a number of times at several different power levels and it is not an issue and that is why the decision was made to let it be like it is.

Thank you, if you have any other questions please let me know

So it looks like the cylinders will stay this way due to flexing in the cylinder walls would be weakened by a .020 bore. It would give way to thinner walls flexing which would promote failure.

WAYNES WORLD

9724VF350 11-02-2017 01:10 PM

Well they're response is kind of bs, but they're not completely wrong. I assume they just ran a hone in your block. The only way to make it go away is to bore to .020. It's nothing that they did incorrectly.

Snedge 11-02-2017 01:20 PM

Quote:

Originally Posted by 9724VF350 (Post 2642583)
Well they're response is kind of bs, but they're not completely wrong. I assume they just ran a hone in your block. The only way to make it go away is to bore to .020. It's nothing that they did incorrectly.

That was established early in the thread.

It looks to me like there was a set of standard pistons coated and waiting on the machine work. So kind of ass backward. The machine shop had to work with what they had to work with.

I'm sure piston to wall clearance is on the loose side, but hopefully not too loose.

9724VF350 11-02-2017 01:45 PM

Hitting them with a berry hone after rigid honing is time well spent to eliminate questions.

Snedge 11-02-2017 01:53 PM

Quote:

Originally Posted by 9724VF350 (Post 2642590)
Hitting them with a berry hone after rigid honing is time well spent to eliminate questions.

LOL
Agreed. It would look way better than an "eyebrow", and this thread would have never happened.

biggy238 11-02-2017 04:08 PM

I thought that at first also, but didn't want to suggest it out of turn. I berry honed the **** out of mine...


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jasonc 11-02-2017 05:16 PM

It needs to have loose piston to wall clearance anyway, I know you run it hard. Is the reason for the rebuild cause it stuck/scored a piston?


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