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Rebuild or run high milage 4.8?

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Old 03-16-2017, 08:46 AM   #1
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Default Rebuild or run high milage 4.8?

Hey all have a question I hope some can give there input on.
I picked up a 4.8 al stock 4.8 with what I can only assume to be accurate miles 260,000.
Currently running should I tear it all down and rebuild?
Or should I check compression just throw a cam in there fresh the seals.
And just run it till I have an issue.
Any input or opinions would be great.
Thanks.
This will be a daily I am throwing in my currently 4.3 Sonoma.
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Old 03-16-2017, 08:50 AM   #2
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Yeah, go for it. If you have the funds, freshen it up before dropping it in so that you can eliminate some potential problems before the install.
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Old 03-16-2017, 03:56 PM   #3
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I really don't have the funds to have someone rebuild.
I would have to do it my self as i have the time and money.
Never rebuilt an ls before that's why i am a little hesitant to tear to far into a currently working motor.
But on the flip side i would hate to not rebuild it and 6 months down the road have a major issue.
That is why i wanted to see how many were running high mileage engines.
And see if i would just be good replacing oil pump, timing chain ,water pump,Basically everything but the pistons and bottom end.
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Old 03-17-2017, 08:43 AM   #4
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People get a way with it all the time and some don't. I just got a Gen III 4.8L that I'm rebuilding with Gen IV 5.3L internals. After tearing down the 4.8L, I'm glad I didn't just run it as is. Some of the rings were seized in the pistons from all the carbon build up, which probably would have caused it to smoke, or at the very least, have some excessive blow by. Lots of sludge in the oil passages too, which could have caused low oil pressure and really done some damage. It was $150 for the shortblock so I can't really complain.
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Old 03-17-2017, 08:52 AM   #5
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I think at very least i will pull the heads and make my decision from there.
I have just never rebuilt anything other than a lawnmower engine before i know this one was currently running before the truck was wrecked and after. I would just hate to tear to far into it and realize i am over my head or put something together wrong and not realize it until after it is in the car. But with 260 thousand miles on it its any ones guess as to how long it will last.
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Old 03-17-2017, 09:16 AM   #6
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It really depend on how it was maintained. I recently tore down a running 6.0 that had 385,000 (that was given to me. All it had was a lifter tick). The cross-hatching in the cylinders looked great and had none of the other things KCS mentioned. I am a firm believer that if you run good oil and change it often these motors can go stupid miles.
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Old 03-17-2017, 09:27 AM   #7
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From what i can tell it looks like he maintained it.
it has an ac delco filter on it.
It had a replaced starter.
It looked like it had replaced intake gaskets.
I will probably pull the heads and see what it looks like underneath and go from there.
When i get that far i will probably post pics and see what everyone says.
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Old 03-17-2017, 09:37 AM   #8
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Remove valve covers and valley cover....
1st pic is the 317 heads off the 385K 6.0
2nd and 3rd pic is of a poorly maintained 5.7 w/150K
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Rebuild or run high milage 4.8?-dsc04219.jpg   Rebuild or run high milage 4.8?-dsc04533.jpg   Rebuild or run high milage 4.8?-dsc04532.jpg  
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Old 03-17-2017, 09:41 AM   #9
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Wow that's crazy i have to get mine out the back of my truck and on the stand but when i do i will post pics.
Thanks for the pics i hope mines not at bad as the 2nd and 3rd pic.
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Old 03-17-2017, 10:02 AM   #10
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People think I'm absolutely crazy, but everytime I buy a truck that I intend to pull the engine out of, I let it warm up to temp. Then I get a very small vacuum line, hook it to the intake, put a bolt under the throttle cam to make it idle at 4 grand.....

and I drop that vacuum line into a full gallon jug of windshield washer fluid.

Takes a few minutes to suck it dry. Using a bore scope, the carbon buildup is significantly reduced. Compression tests almost always yield better results, which is a sign that it helps with stuck rings.
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Old 03-17-2017, 10:15 AM   #11
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that's more or less what your doing with sea foam cleaner.
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Old 03-17-2017, 10:18 AM   #12
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Except its FAR cheaper. It takes 2.5 gallons to equal the cost of a can of seafoam. Seafoam doesn't work nearly as well if you suck it into the intake. It does a better job if its tossed in the oil or gas tank. There just isn't enough in that small bottle to make a difference in carbon buildup unless you pour it into the cylinders and let it sit for a while before firing it back up.
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Old 03-17-2017, 10:47 AM   #13
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Definitely open it up, you'll need a torque wrench to reasswmble, but ls's are super super easy to work on, I mean really easy
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Old 03-17-2017, 06:55 PM   #14
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When i got my 5.3 it was by FAR the worst engine ive ever seen the inside of. Literally a half inch plus of sludge in areas. 218k when i got it.

I pulled it apart, cleaned it and scraped all the crap off. Blew the oil channels out with my pressure washer, brake clean, and my air compressor.

Put a set of 40.00 rings in it (mahle's) and cam bearings in it (they were gone)

Ran it for a year and a half in a boat, put 16 bottles of nitrous through it and it still was turn key at the end of the season. I built a new engine because i wanted a new engine

moral of the story... Pull it apart, clean it if needed, run it... you might be in it 500 bucks... Buy the how to rebuild LS engines book from amazon

When i got it:










After cleaning
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Old 03-17-2017, 07:02 PM   #15
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^ i've got a couple of them that bad.

it's like people are trying to turn the motor oil back into crude oil.
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Old 03-17-2017, 07:26 PM   #16
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Steves86ta did you hone the cylinders or just slap new rings in?Thanks for the pics and info on the book.Will look into it.
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Old 03-17-2017, 07:32 PM   #17
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Steves86ta, you win! That is the nastiest engine I have ever seen!
Someone must have NEVER changed the oil....
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Old 03-18-2017, 12:40 AM   #18
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Yeah it was nasty

I dingle ball honed it and ran the living poop out of it
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Old 03-18-2017, 06:42 AM   #19
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My 140K mile LQ4 looked great until I pulled the heads. The cooling passages were so crapped up with gunk and rust it was enough to push me into a rebuild. I knew I wouldn't get it clean enough that I would feel good about hooking it up to a new $800 swap radiator. Now of course the rebuild has turned into a $10K 403 stroker so go figure....
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Old 03-18-2017, 07:51 AM   #20
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Quote:
Originally Posted by steves86ta View Post
yeah it was nasty

i dingle ball honed it and ran the living poop out of it

yess!!!!
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