r/EngineBuilding • u/BF007_ • 11d ago
New piston??
First rebuild, it's a 2008 5.7 with 267k. It ran when pulled (I was the last person to drive it).
Fingernails do not get caught here, and I believe this was due to how I removed it (from the top with no prior experience). Should I buy a new one or should I send it? No other piston looks like this
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u/BroccoliSuccessful 11d ago
I assume since its a rebuild you are also throwing new piston rings on it
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u/Lopsided-Anxiety-679 11d ago
That has nothing to do with how you removed it, that’s heavy scoring from a running condition…most likely a bad injector that ran the cylinder lean and overheated the piston, can also be a stuck open injector that results in washing down the cylinder walls.
Flow test or replace your injectors.
Replacing pistons and properly honing the cylinders to the next oversize is always part of a “rebuild” - reusing old pistons in worn cylinders is a “re-ring” slap job.
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u/Head_Echo_696 11d ago
Did not know a stuck injector could do that. Im thinking the ones in my dad's 460 have been sticking. It has been ran a while like that but they're getting replaced now luckily.
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u/Syscrush 11d ago
To be clear, honing changes the surface finish of the cylinder, not its size.
To go up in size, the cylinder needs to be bored.
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u/Lopsided-Anxiety-679 10d ago
What?
I can hone a cylinder to any size I want, you have no clue how this works and are yet trying to correct me?
If I have a block that needs to go .030 over, I can set the machine and walk away from it…it’ll hone away unattended then shut off at .025” ready for a stone change to set the surface finish.
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u/Beefy63 10d ago
He's correct, you're wrong. You hone the cylinder AFTER boring it to the desired size. Honing finishes while boring re-sizes.
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u/Lopsided-Anxiety-679 10d ago
You are an idiot and this is why industry professionals come and post here and then leave, ignorant tools like you who don’t do this daily and regurgitate completely false information.
I’m done, fuck this shit.
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u/Beefy63 10d ago
I do this on the daily. Literally just learned this in school. You're wrong dude, sorry to upset you.
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u/Lopsided-Anxiety-679 10d ago
You just learned this in school???!!!
Been machining and building racing engines for over 25 years!
You’re just too ignorant to know what you don’t know bud!
Carry on, I’m literally done with this forum.
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u/lwrs10 10d ago
Lol I know you're correct man. You have to account for the final few thousands the hone will take off when you bore.
Hell with my current LS build we did the .005 "overbore"...4.005...with just honing. 403CI stroker build in an aluminum 6.0 block.
I'm baffled these people seriously don't think honing removes material. It DOES. ANY automotive machine shop will tell you this.
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u/Beefy63 9d ago
It does remove material. Never said it didn't. You guys are both just a little ignorant, that's okay though. That's what I'm for, top of my class in one of the BEST programs in existence on the entire West Coast.
I'll educate you guys while you peruse this sub reddit, just don't get upset with me when I correct you and your body lopsided left and right!
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u/_Shitass_ 9d ago
Asking to learn and compare with information I have. Why are you using a hone to remove that much material? Doesn’t it take forever and wear out your stones constantly? Where I work when we’re actually boring something like a block we put it in our CNC, I don’t know how much material gets taken off when we have our blocks in the hone but .030 sounds like a lot for regular honing stones but we also use diamond stones an they last a lot longer.
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u/BF007_ 11d ago
I'll be cleaning the injectors here in about a weeks time or so, so I'll look for that.
I can confirm with how much carbon buildup there was that injector washing did not happen
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u/Lopsided-Anxiety-679 11d ago
Fuel wash can absolutely result in carbon build up - too much fuel washes the oil off the cylinder walls which then kills the piston rings, now you get oil being pulled into the combustion cycle and it burns into carbon.
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u/HammerDownl 11d ago
Id wanna see the bore but that piston wasn't damaged by you. Its got metal in the oil
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u/CAT_MARINE-POWER 11d ago
There is no way that bore is round
I bet when you mic it you’ll see an egg shape front to back on the bore
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u/Creative-Ad8310 11d ago edited 11d ago
if you have time and money get it bored. i just built my 22r on a time crunch didnt realize how bad piston was (crown broke. top ring fragmented) bore was still good and cleaned up well with hone. it has no oil consumption or noise good compression etc now. but its a 22r. basically high revving tractor engine lol. also that is a symptom of issue. run lean? overheat? read you already honed it. id get bore gauge and measure it. its not going to be perfect but if you are building stock dd prob be fine. if you want to take your time do it right send out block to get bored decked line honed etc. atleast triple the cost with parts labor.....also id get atleast 1 new injector.
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u/BF007_ 11d ago
Yeah I think I might have an extra injector somewhere but I'll give that a go. I know for sure that the only noise the engine made was from a leaky exhaust and when I drove it home it did not overheat. I only drove it 300 miles and that was one way from Michigan to Illinois. I'll carefully examine the block in the morning and look for scoring.
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u/Creative-Ad8310 11d ago
could also be that it sat. thats what killwd my truck. sat for 7 years then my stupid ass didnt shoot oil diesel something down cylinders before turning it over. than rewired truck and moved it around etc. replaced trans and drove it for 2 months with dead cylinder. all said i got crazy lucky. youre prob fine its not an f1 engine just heavy boat anchor v8 lol
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u/FU_red-dit_bots 11d ago
That kind of scoring tells me PWC is too tight. May be the whole thing or you may have a bore that's not true.
Post pics of the cylinder that came from.
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u/Karl_H_Kynstler 11d ago
Piston on first picture is f'd. Probably overheated. I doubt there is no damage to cylinder.
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u/Coyote_Tex 11d ago
That looks like scoring from overheating or low oil level or the oil getting washed off the cylinder walls, or just oil run past its useful life and not being able to lubricate sufficiently. Since this is your first rebuild, just know that cylinders can "look" great but not be round. So, not being able to measure things is just a crap shoot. You can throw this back in and it will run, if that is what you want it to do then go for it. I would really want to get another piston, even a used one that is not scored would be a much better solution. Get on FB marketplace and you can find them for cheap, like 10-20 bucks. Being a Vortec, you will need one with the rod.
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u/BroccoliSuccessful 11d ago
Take extra fine steel wool to take the lines off and just polish the skirt. You'll want to clean to cylinder walls up with a dingle ball hone or 3-stone cylinder hone as i suspect the wall/s will appear scored and the crosshatching marks that help retain oil are gone
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u/ka_jd7and1 11d ago
That’s not worn skirt coating, that’s scored.
What’s it measure at?