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2004 CM7 Accord - K24A4 - 5 Speed Manual
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Discussion Starter · #1 ·
Hey Y'all

I don't have much to give in terms of a story this time. Since this is my first time pulling apart an engine, I'm not really sure what I'm looking at. I just get the feeling that it's not great

All kinds of oil varnish on the piston, the rings look to be in good shape though:
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Not really sure what to make of this:
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This is pretty representative of the bearings on all four pistons. they all have these black spots and odd areas of discoloration:
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the real kicker, however, was the state of the mains. the side with the oil passageway looked fine, as expected
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But, the non grooved side decided it was gonna make its own grooves. not good as far as I know
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lastly, here are the bearing seats on the block and girdle. along with the crank journals (which I forgot to take pics of), they look suprisingly decent. not that it matters, since I'll be using a different block
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so yeah, what do you all make of this?
 

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Lotus Elise K20A2
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pistons:
p2w clearance was a tad too tight or the piston temperatures too high.
scratches are from debris, so oil coke or poor air filter performance.
Given the milage, they look OK.

bearing shells:

The deep scratch in the mains are usually caused by debris in the oil. You also need to check the crank if there are burrs on the oil hole.


The rod bearings look bad. Would you be able to post a picture of the journal facing side of the the bottom rod bearings?
The convex surface is less interesting as nothing should move there. Discoloration could plainly be oil contamination making its way into that tiny gap over time and being worked as the shells are loaded.

From the look, it seems the rods are bend and twisted or the rod eye is distorted. Could have been overrev'd or slightly hydrolocked. Excessive rpm would rather distort the rod eye and cause two wear strips per side as the bore is now oval.

 

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2004 CM7 Accord - K24A4 - 5 Speed Manual
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Discussion Starter · #3 · (Edited)
the likelyhood of debris in the engine is decently high for various reasons, most of which are due to poor assembly of various componants on my end. however, I think the majority of the damage was caused by oil starvation from two occurances, where I drove the car unknowingly with serious oil leaks. this only took place over the course of <5 miles/<20 minutes of total engine running time, but still is likely the cause for such extreme wear on an otherwise well maintained engine

The rod bearings look bad. Would you be able to post a picture of the journal facing side of the the bottom rod bearings?
The convex surface is less interesting as nothing should move there. Discoloration could plainly be oil contamination making its way into that tiny gap over time and being worked as the shells are loaded.
I'll post pics when I get home from school. from what I remember, the crank journals looked good, but I didn't give them a thorough inspection.

EDIT: I also read what you had said on a seperate post about momentary pressure drops with long left-hand turns. lets just say that where I live, alot of highway on/off ramps involve left hand turns, and that I took them rather spiritedly...
 

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pistons:
p2w clearance was a tad too tight or the piston temperatures too high.
scratches are from debris, so oil coke or poor air filter performance.
Given the milage, they look OK.

bearing shells:

The deep scratch in the mains are usually caused by debris in the oil. You also need to check the crank if there are burrs on the oil hole.


The rod bearings look bad. Would you be able to post a picture of the journal facing side of the the bottom rod bearings?
The convex surface is less interesting as nothing should move there. Discoloration could plainly be oil contamination making its way into that tiny gap over time and being worked as the shells are loaded.

From the look, it seems the rods are bend and twisted or the rod eye is distorted. Could have been overrev'd or slightly hydrolocked. Excessive rpm would rather distort the rod eye and cause two wear strips per side as the bore is now oval.

I tend to agree with this. At first the pistons looked like there might have been too much varnish, but the rest of the block looks normal for the age. i think this supports the piston temperature getting too high... the oil flash burns onto it. maybe a tune that is slightly too lean.

the bottom of the first bearing looks like one from one of the motors i have spun a bearing in. that could have caused the debris ...but all of that combined it looks like it was over revved to me.
 
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2004 CM7 Accord - K24A4 - 5 Speed Manual
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Discussion Starter · #5 ·
the bottom of the first bearing looks like one from one of the motors i have spun a bearing in. that could have caused the debris ...but all of that combined it looks like it was over revved to me.
I'm assuming you're refering to the rod bearing? I'm not sure about over revving since the stock tune limits the motor to 6700 RPM, but that may be considered over revving for the bearing clearances?
 

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you can mechanically over rev an engine, say on a missed shift, a high rpm clutch kit, and even a hard pull with the stock pull (it limits the fuel but it doesnt limit the engine speed immediately).

I know my engine has seen 10k RPMs accidently on the race track... seems fine :LOL:
 

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Discussion Starter · #7 ·
you can mechanically over rev an engine, say on a missed shift, a high rpm clutch kit, and even a hard pull with the stock pull (it limits the fuel but it doesnt limit the engine speed immediately).

I know my engine has seen 10k RPMs accidently on the race track... seems fine :LOL:
There was a time, actually, where I was doing some launch practice, and the ecu did a hard cut at 5000 RPM or so. I never quite figured out what happened, but this seems to fit the description
 

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Lotus Elise K20A2
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it all will need a good clean. The crank journals might need some polishing.
Please remember to add a light coat of oil, best anti corrosion oil, on all iron parts after cleaning. Otherwise, they’ll rust.
 

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Lotus Elise K20A2
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The surface that faces the crank journal.

The shell on the opposite side of this photographed the same way:


The back side of the shells is less interesting unless there are foreign objects embedded or the shell has spun.
 

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wow.
are these Honda OEM bearing shells?
My first impression is that you were running excessive rod bearing clearances. This led to increased wear on the top half as it was running only in the centre and cavitation on the bottom half from the journal lifting up on the bottom side during the beginning of the up stoke.

This could also happen if someone dropped in some std size ACL shells without measuring clearance or by not torquing them up properly. This also leads to increased clearance. But then this would also lead to rod bolt failure.
 

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Discussion Starter · #20 ·
wow.
are these Honda OEM bearing shells?
My first impression is that you were running excessive rod bearing clearances. This led to increased wear on the top half as it was running only in the centre and cavitation on the bottom half from the journal lifting up on the bottom side during the beginning of the up stoke.

This could also happen if someone dropped in some std size ACL shells without measuring clearance or by not torquing them up properly. This also leads to increased clearance. But then this would also lead to rod bolt failure.
would you believe me if I told you these were Honda? They have to be, the car was stock when I got it
 
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