So I scored what I thought was a home run. A 6.0 lq4 with ls3 heads for what seemed to be a good price. Was told it was running when pulled from the vehicle to make way for a larger motor. Well I had no special tools on hand so I bought the motor seeing only what I could see. Once I got to the house I pulled all the rockers off to close all valves and went down the line checking all for leak down. Seeing 90% leak down on 7 cylinders made me sick to my stomach. Only one had less than 20% leak down. So I pulled the heads and noticed in my opinion some bad scoring seems to be mainly where the piston skirts ride. I’ve done bolt ons for years and swapped heads but never really gotten into the bottom ends until now. Below are some picture of the scores I am talking about and would appreciate any input in what my next step should be? Maybe worth having a machine shop look it over or cut my losses and maybe salvage the ls3 heads?





Any help is greatly appreciated

 

Any idea what the current bore size is? I recommend sending the short block to a reputable machine shop and see what they have to say. Most likely it will need to be bored and honed to the next size up and you'll still be able to use the crank and rods.

 

So I measured to the best of my ability with a digital micrometer as deep as it would let me measure and I was getting 3.998 and 4.000 I would really have to crank on the micrometer **** to show 4.000 inches however I know that’s not the correct tool for the job but it was all I had but off that measurement I would assume it’s a virgin block. And could be able to handle a hone and possibly a bore. I have not called around any machine shops yet but before they go straight to honing or boring do they typically inspect the block for other failures? By the way thank you for your reply. I can’t tell you how sick I felt when I saw those score marks

 

Can you feel those marks with your finger nail? It is hard to tell from pictures if they are bad as they look.

 

Hey wretched, yeah I can feel them with my nail. It’s not enough to catch my nail and stick but I can difinitly feel them. And when I wipe the cylinders with a rag the score marks will grab lint and fibers of the rag where it just wipes smooth on the un scored part of the cylinders. And you can difintly feel the difference in the surface dragging your finger tip around the bore.

 

Based on leak down I'm pretty sure the cylinders are ring scorned. Best bet is to get it over to machine shop to see what needs to be done in order to get the block ready for a rebuild. I'd take it .030 over start looking for some 4.03 bore pistons or you could get it sonic tested to see if it's capable of going to an LS3 bore and go that route.

 

Sounds like going to the machine shop is your best bet. They should be able to tell you if a hone can get it right or if a new bore is needed. Based on that, order new pistons, Then the machine shop will bore accordingly for the pistons.

 

When doing the leak test, where do you hear the air escaping?

 

Yeah good question. If the rings are in fact shot the pistons would have been caked with burnt oil and the plugs fouled to hell. If the plugs were in it at the tine which they should have been and it was rings you'd be hearing it through the crankcase. Could it be that the cylinders and rings are fine and the problem is with the, valves, seats or seals. There's some serious scuffing there though and I'd be concerned about it.

 

1. Shame the seller wasn't honest. Is he/she is willing to make it right? If not, shame them. You're not doing them any favors if you don't. That motor wouldn't run without compression.
2. Appears it's been rebuilt. Piston to wall tolerance or rings/gap too tight? Maybe overheated and caused scoring? Need to disassemble to better understand what's up.
3. Did you get a build sheet to know what was done during rebuild? or... was it sold as stock 6.0? Piston appears to be a GM .5mm oversize 89017849.
4. Let us know what you find.

 

May I ask what you paid for it?

Thanks.

 

It's one of those trick motors. You know the choo choo engine passed off as a freshy that was dismantled, cleaned and slapped back together. That's too pristine inside there to have been a running engine.

 

Thanks for all the input. So as far as where I heard the leak was definitely the crank case passing the rings. It’s only as clean as it is bc I cleaned it up to get a better look at the pistons to see if they were stock or not. From what I’ve found it’s actually the ly6 and not the lq4. A gen IV motor supposedly better rods and They came factory with valve reliefs cut in them to accommodate the vvt. They have 9805 stamped on the tops which also comes back to show that they are original pistons. I beleive. I have a machine shop locally that says they will mic the cylinders at no charge and check it out to see what it may need. I already planned on doing rods and pistons any how but wasn’t planning on the block needing attention. I may have over reacting by posting this thread as I was sick after I found what I did but describing it to the machinest he thinks I may be able to get away with a block hone. But I will keep you all updated with the out come. Don’t think the seller is willing to do anything about the condition of the motor I guess it is what it is. As far as price I paid $1200 for the long block and the scored cylinder walls were free lol

 

I’ve seen a tune cause cylinders to look like that. A really rich condition will cause the cylinders to “wash down” and top ring will scuff the walls from lack of oil.

 

Sorry to hear that, could of been a lot more, but on the good side you do have a 6.0L with rectangle heads, with the "good" rods. I would try to find some take out LS3 pistons, have the block bored to 4.065", and have an iron LS3 for way less then aluminum 6.2, just saying.

Stampede.

 

I agree with you mod squad It spend a lot of time on the dyno getting tuned on probably so much its probably what caused exactly what your talking about. Also this is what I recently found out today after I talked to the guy that removed the engine was that they had an -an fitting for an oil feed line coming out of the the oil pressure sending unit location that was capped off with a plastic ac Schaeder valve cap pouring oil out an That oil pressure cold was great 40lbs + but at temperature 10-15lbs. I love how I find all this out after the fact that I now own it.

 

So I can take criticism I payed $1200 did I overpay? I’m in ga and junk yard 5.3s are around 600-800 lq4 1200-1500 an this is normally no computer or harness or accessories. Honestly I’m trying to justify my purchase lol

 

I'm saying it's not that bad really, look at this way, you paid $500-600 for rectangle heads with rockers, you paid $500-$600 for short block with the good rods, that needs work. Like I said earlier find some good used LS3 pistons, bore the block out to 4.065", can't cost that much for machine. I'm just saying it's not that bad, not great, but not that bad.

Stampede.

 

1200 is a bit steep for what's essentially a core to rebuild now. I got porked on a LS1 locally once. Guy said it had lifter tick, machanic pulled the engine for a 6.0 and swapped it into his f body. I bought it, got home and started dismantling it. Lifter wheel was trashed and broke into pieces, snapped the camshaft and twisted part of it, broke a chunk of the piston skirt off on two cylinders and cracked the a couple cylinders. Looked like a grenade went off under the windage tray.. but I'm sure his mechanic didn't see any of this while swapping oil pans..

 

The cylinder walls and rings are too gone for that to ever run properly. But it almost looks like a flex hone with power drill could possibly hone the cylinders good enough to remove those scratches. After you hone it clean the bores thoroughly with brake cleaner or similar until a paper towel no longer gets dirty. Install new rings properly gapped and assemble with the correct lube. This is if you want to spend the least amount of money on it.