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Engine Knock

2436 Views 28 Replies 7 Participants Last post by  sperkins525
November 29, 2022
Driving up interstate and started doing this, the thing that has me confused is it's kindve rhythmic on and off but was getting considerably worse till I got home.
Talked to reputable local shop and he suggested trying injector cutout but could not tell any diff.
Currently have injectors pulled and inspected with borescope and looks like #4 piston has valve marks in the top.
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Head off, #4 piston was kissing the head, hardly anything to see but obviously the issue. Hopefully have engine pulled tomorrow.
Rebuilding yourself or what’s the plan?
Yes with technical help from my brother who does mechanics/rebuilds on farm equipment.
Surprisingly with the wimpy junk piston design and running egt's around 1450° the pistons don't have the slightest sign of melting and there's no scoring on the cylinder walls.

It's obvious someone was in the engine before this and I kind wonder if someone did a slap it together send it down the road job or why else I'd be having this issue with only 8600 engine hrs
Wimpy junk piston design….I think someone has read the internet too much🤣

I would suggest getting a Cummins manual. Has everything in it, everything. I don’t know how they sell them today, mine are two books and a cd that I’ve never used, might only be a disk these days. But every procedure is covered. Good info.
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Well i like to just go by what feels right and if theres any question with that I will look no further than the mob rule on CF lol.
JK we will definitely go off the proper cummins specs.
Well #4 definitely spun the bearing and there already .25 oversized
Tire Hand Automotive tire Wood Wheel

Finger Nickel Household hardware Material property Thumb

And here is what #3 looks like. And they are King brand.
Fluid Water Gesture Finger Gas

Leg Musical instrument Wood Tints and shades Font

What makes spots like that??
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It looks like #4 has a score in the cylinder wall we need to determine if it's already been oversized and whether we can hone it out.

I'm thinking about swapping a 6.7 short block in, what size turbo is needed for a swap like this.

Any thoughts or comments be free.
What makes this, these things are hammered
Automotive tire Rim Gas Motor vehicle Nickel
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Well this thread seems to be totally dead, so i guess I'll keep going solo.

Called machine shop and they wondered if this was a hotshot rig, they said they've seen hotshot guys running heavy loads at high rpms have this issue.

They recommended using performance bearings so I guess Mahle here we come, I'm going to use the H rated bearings.
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Oh man those bearings are shot. What in the world.

I would 100% recommend dropping a 6.7 in. I’ve done both my trucks and it’s the best thing I’ve ever done next to tuning. You can run the factory 5.9 turbo just fine, it will spool and drive great.

Noticeable increase in torque, and added airflow to support larger turbos, better. Meaning what would be laggy on a 5.9, isn’t on a 6.7.
Well the problem is I think the block is fine if we hone it. I'm not trying to do a budget build necessarily but not sure I can justify swapping in a 6.7.
Am I correct in thinking the 6.7 has the same size rod journal as the 5.9?
How does the 6.7 ever hold up to the HP there coming out the factory with?
Where did u find your 6.7 short block? I can't really find anything decent for less than 5k and I would definitely brake into it and check it out before just dropping it in, which could potentially be another thousand or two
Waited half a week for a used rod because the new one we got was way out of weight compared to the old ones.
Now I open the last piston pack and prepare to oil rings and install this afternoon and this is what I get.
Mahle pistons came with rings installed from XDP.
Now I'm waiting for next business day (Monday) to see what they have to say for themselves.
Drinkware Gas Nickel Rim Cylinder

Automotive tire Motor vehicle Bumper Alloy wheel Rim

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Missing something, lol!!! Sorry Man, that's unacceptable and they should cut you some money back!! After they ship you the rest of the rings! Jmo✌
I'm trying to not be absolutely bad at them but I just can't help it.
That sucks.
I guess if it's not one thing, it's another.
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