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Old 12-05-2018, 03:16 PM   #1
LeedomtoFreedom
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Default Some interesting stuff while doing headgasket.

Take a look at this

[IMG][/IMG]

[IMG][/IMG]

Is this normal...?

Just kidding, is there anything I should do before throwing it back together, going 16v in a bit and will probably get another short block / new piston but need the car running for now.

Only happened on this one piston. looks like a chip flew through there. Car ran fine before the gasket leaked coolant but the it wasn't the same cylinder that leaked.
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Old 12-05-2018, 03:19 PM   #2
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FOD!

I'd clean up any sharp burrs that stick out (if there are any), but otherwise not worry about it. Small bits of metal sticking out could get hot and encourage detonation.
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Old 12-05-2018, 04:07 PM   #3
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Amazing how these can keep running even with a chunk of something bouncing around in there.
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Old 12-05-2018, 04:09 PM   #4
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Old 12-05-2018, 04:15 PM   #5
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The marks are detonation marks, not foreign matter..Classic shape.
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Old 12-05-2018, 04:56 PM   #6
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Quote:
Originally Posted by John V, outside agitator View Post
The marks are detonation marks, not foreign matter..Classic shape.
Based off of my experience (which we all know no one (especially you) gives a **** about), this is not detonation, but rather something got ingested.
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Old 12-05-2018, 05:44 PM   #7
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It sure looks like dents from a foreign object (I'd say probably a spark plug bit). I managed to ping a motor half to death once and the pits on the piston and head didn't look like that. They were rougher looking, grainy pits, not sharp-edged little punch mark dents.

And the (cast iron) R-Sport pushrod head I got had sucked in a small nut from the DCOE's - one cylinder had all sorts of tiny little dents that looked about like that as well.

But I suffer from a small sample size.
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Old 12-05-2018, 06:28 PM   #8
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Uploading some better lit pictures. Definitely looks like something fell in there. The gouges are deep and in one, there was a some material that seemed to have been pushed towards the head.

[IMG][/IMG]

[IMG][/IMG]

[IMG][/IMG]
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Old 12-05-2018, 06:39 PM   #9
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The nordic engine destructo gods approve. Looks like the top of the piston was banging on the cylinder head. Was that a tight squish engine? Maybe the impact was breaking off small pieces of aluminum from the head and the piston?
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Old 12-05-2018, 08:21 PM   #10
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So that gold Volvo that I tried destroying..it would knock/detonate worse than any engine I’ve ever heard in my life. Not sure if it was cus of the coolant injection through the block or what. But I’m talking audible even with the radio up..

Anyway, this is what the head looked like.
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Old 12-05-2018, 09:18 PM   #11
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Quote:
Originally Posted by LeedomtoFreedom View Post
Uploading some better lit pictures. Definitely looks like something fell in there. The gouges are deep and in one, there was a some material that seemed to have been pushed towards the head.


Come on guys...its detonation marks..it always looks like some rectangualr small thing..
Think and look, don't argue..
Think why was the 'thing" only banging into the flat part of the piston and quench pads on the head is it was something bouncing around the head with enough force to make those dents?

It would be marked up EVERYWHERE in the whole chamber and all across the piston crown in about 1 second.....or 2...2 seconds at 3000 rpm would be hundreds times banging that sh!t around randomly...everywhere..

It is classic det marks..anybody who ever raced 2 -stroke ought to be able to confirm that IF they ever pulled the head---(in those it is always in the quench area also)
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Old 12-05-2018, 10:03 PM   #12
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.

Last edited by bobxyz; 12-06-2018 at 12:41 AM.. Reason: MTBGA
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Old 12-05-2018, 10:27 PM   #13
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Quote:
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Huh? The sharp, deep gouges could only come from something solid being wedged between quench pad and piston at TDC, but you could argue why it stays near the exhaust valve instead of showing up on the other quench pad too. Just bouncing around in the main open chamber isn't going to do much damage. If it had a much more melted look, I'd suspect detonation first.
Whatever, believe what ever you want.. It's clear "classic" det to anybody who has been in the business a while.. There are NO marks anywhere except in the flat surfaces--and their edges..

[IMG]
https://www.thehulltruth.com/attachment.php?attachmentid=446598&stc=1&d=1407701830[/IMG]











Why show so many 2 strokes?
Cause they have GIANT wide open holes EVERYwhere and some little foriegn matter simply goes out any of the holes, biggest being the exhaust port which is maybe 1/2 the height of the bore and 60% of the circumference and a BIG hole..And since they fire every time the piston goes up, getting jetting, or plug heat range wrong is 2 times the problem and things are more dramatic. So if your engine swallowed even large hunks of metal..it usually just goes poof out the hole..but with det it quickly leads to what you see above.

Try looking at Google images for serious sites..Not well meaning fans with well meaning friendly advice type places.

Last edited by John V, outside agitator; 12-05-2018 at 11:11 PM..
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Old 12-05-2018, 10:43 PM   #14
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Last edited by bobxyz; 12-06-2018 at 12:41 AM..
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Old 12-05-2018, 10:49 PM   #15
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[IMG][/IMG]
Cleary, engine has ingested a staple, you can see it at the bottom of the pic...


While JohnV makes an excellent point about why FOD would be all over instead of limited to one side, I'm going to defer to PromiseRing/McLovin's vast experience and knowledge base.
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Old 12-05-2018, 11:11 PM   #16
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I support John's analysis. Looks like detonation to me.

[IMG][/IMG]

Check the shoulder of the piston... edge eaten away.

Last edited by swedefiend; 12-05-2018 at 11:20 PM..
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Old 12-05-2018, 11:27 PM   #17
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I would think detonation also, unless there was no air filter, it would have to be a decent sized, pretty tough chunk of something to do all that. Unless it was an internal part that let loose, I assume the valve keepers are still all there haha?
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Old 12-05-2018, 11:46 PM   #18
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Is the damage only in one cylinder? If so, which? If it’s detonating that bad on just 1 cylinder, i think you’re probably lacking fuel or something severe. That is BAD damage. Also, you should listen closer for knock. And do you have a wideband?
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Old 12-05-2018, 11:57 PM   #19
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Quote:
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Also, you should listen closer watch for knock.
Knocksense

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Old 12-05-2018, 11:59 PM   #20
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I'm inclined to say that is foreign object ingested, compressed a few times, mostly blown out after a few strokes, and then a few small pieces stayed and did a little more damage. Detonation would have more crater-shaped indentations, at least from my understanding of the behavior fuel under compression.

HOWEVER
The markings on the quench area of the head make me second guess the ingested foreign object theory.
The race engine I've torn down that had detonation was similar to the above. Aluminum metal, when heated, will burn and could create sufficient carbon particles to further gouge out the grooves. The detonation could've been exaserbated by small burs from initial damage in the head and piston.

I defer to John's analysis due to his experience as well as my own, though I'm extremely curious either way.
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Old 12-06-2018, 12:02 AM   #21
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Quote:
Originally Posted by swedefiend View Post
I support John's analysis. Looks like detonation to me.

[IMG][/IMG]

Check the shoulder of the piston... edge eaten away.

Imagine the side of the piston...yikes...
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Old 12-06-2018, 12:04 AM   #22
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2nd statement: now staring closely at that picture, I can see pieces of the piston crown missing. Detonation, followed by piston chunks further gouging the head and piston.
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Old 12-06-2018, 12:10 AM   #23
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Originally Posted by vwbusman66 View Post
2nd statement: now staring closely at that picture, I can see pieces of the piston crown missing. Detonation, followed by piston chunks further gouging the head and piston.
OoOoh good point there too!

OP, there is no way you didn’t hear this thing knock. You need quieter exhaust or knocksense.
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Old 12-06-2018, 01:57 AM   #24
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Quote:
Originally Posted by apachechef View Post
[IMG][/IMG]

Cleary, engine has ingested a staple, you can see it at the bottom of the pic...
Uhh..... no.

Staples are more square-cornered.

This is obviously the letter "C".







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Old 12-06-2018, 02:24 AM   #25
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Quote:
OP, there is no way you didn’t hear this thing knock. You need quieter exhaust or knocksense.
I honestly didn't hear anything. Swear to God.

Probably going to invest in a knock sensor... and muffler. I have a vibrant resonator but no muffler. Not that loud but not quiet.
I also do have a wideband that used to be on the dash but now hides in the glovebox.

The OTHER pistons look much better. One of them is fine but there's a little acne going on. Not nearly as bad as the front-most piston.

I also remember when this engine was in my other car, it once or twice 'kicked back' when under boost. Pretty aggressive kick, kinda like if you were to sidestep the gas then get back on it.

Regardless I'm going to get new pistons soon and either get a new short block or hone the walls if they look good Just was curious what everyone thought.
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