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2008 5.3 LC9 Gen4 engine build gone wrong?? Need help
Let me start by saying I'm a retired tech from gm dealership. Mostly lightline and After cleaning them up. And before sanding them Before cleaning them
r&r crate engines.
Never completely tore an engine down and rebuilt it. Just partial repairs.
Always wanted too, but never really had the time, place or vehicle to do it.
So now i have my 2008 Avalanche daily driver that had developed dod problems and so i decided to pull the engine and tear it down and rebuild new stock parts and delete AFMDoD.
I know the engine has 200k plus miles. Unknown correct miles.
I purchased the
I cleaned the block and heads and measured bores determined i could just refresh with new stock parts.
New Stock GM parts
Pistons and Rods, Camshaft and Crankshaft.
Aftermarket parts
Melling valves and pushrods
Michigan motorsports roller rockers, springs, retainers and keepers.
Should be off to a great start! Nope! I made the mistake of watching youtube videos on resurfacing blocks and heads. This is when my head swelled up and i lost reality and bypassed the machine shop path.
Never in all my 20 years ever did anything like bypass machine shop. Ugg.
I put together a 3/4 15x30 board and routered out 1/8 in hole to fit a 12x24 porcelain tile from lowes. I put the straight edge on it to verify flatness. I have a machinest straightedge.
Glued the tile in the slot and glued 240 grit sandpaper to the tile no overlapping of sandpaper.
A week later me and a friend put each head on the sandpaper tile and pulled back and forth from each side making sure we didn't push down and only pull.
The heads were looking beautiful. We stopped on the heads and put the block on it. Same procedure.
I noticed low spots or areas that were not getting clean. So i grabbed the straight edge and found the heads and block has low spots. I then checked the tile for flatness and it had developed a high spot. O know!
I’m not sure how it developed this but i stopped everything and took the block and heads to the machine shop.
The machine shop said they dont recommend decking the block because they have no way of telling where the specs are at. I was like what, wait Who! O no learning curve ball. What does this mean???
They recommend resurfacing the block and heads just enough to get them flat and using thicker head gaskets. And bore and hone. And rebuild the heads.
And getting oversized pistons with rings. Said the stock rods are fine not to waste money on them.
so I was able to return the GM stock pistons and rods.
But now after looking up going to far on heads and or blocks can cause all kinds of problems. Great now what do i do?! I don’t think the block or heads have ever been touched before me. You can see the numbers still, so doesn't that mean it wasn't decked?
Sorry for the long story but wanted to give as much info i can.
So is this project botched beyond proper repair and buy another engine? No funds for that now.
How will I know the head gaskets are the correct size and will work?
Cant the machine shop know if it’s in spec heights after resurfacing.
This has gone out of my experience and I’m lost.
What a bummer!
How do i get this project back on course?
I don’t have pictures of after the sanding! I can't find them on my phone snd now everything is s the machine shop
You went to a crappy machine shop, that's the second problem. First is using porcelain tile to resurface things. The machine shop can't tell what the specs should be? Deck height on an LS is 9.24". Problem solved. But I'm confused. "Decking" a block and resurfacing a block are literally the same thing. So they say they can't deck it, but they can resurface it? Makes absolutely zero sense. If you have to deck the block too far, it's junk. It is NOT good practice to just throw a thicker head gasket on. Your deck surface will be thinner and more prone to blowing a head gasket or cracking. And the deck shouldn't be just cleaned up enough. What if it takes .005 to clean it on one side, but .020 on the other? Both sides should be taken to the same amount, or one bank of cylinders will have lower compression. As for boring it out, ask them to show you the bore wear, right in front of you. LS engines do not typically wear out bores. If it's not showing excessive taper, run those stock pistons. To ease your mind a bit, I seriously doubt you took enough material off your block to ruin it, and you DEFINITELY didn't off your heads. But you should probably find a different machine shop, because they don't sound very competent.
Also, you can afford to spend what will likely be $1200-$1500+ on machining, but not on a pull-out 5.3? Where I am, you can get a whole truck with a 5.3 in it for under a grand. I got an '06 Saab 9-7X with an aluminum 5.3 for $500. If I were you, I'd cut my losses and find a running pull out engine. This is gonna cost you a LOT more if you go the rebuild route.
Thank you for the response. I think they misspoke before actually doing an inspection. He only quickly looked at them when i dropped off. I went down there and he thought I said it’s been decked already. They were busy when i dropped it off. Could just be my inexperience and there busyness that i may have gotten confused. Still I thought the machine shop could tell if to far gone and if salvageable. So when he said there was no way to know how much was takin off and what the spec was, i was confused. I barely know how to use my dial indicators, bore gauge and etc, I thought they know this stuff like nothing else.
So all the other shops are 3 months out and contract work comes first. So i went here when they said we can take it. They have a good reputation. I was refered to them by multiple people.
I’m hoping its just my inexperience on rebuilding and misinterpreted also.
I want a new engine for another 200k is all. And Ive always wanted to try this for the first time.
I guess i should of stuck with what i do know. R&R crate engine.
Well I’m sticking with this and wait to see what they say and do. Oh he also said he would verify the bores first also. He just wanted to know what all i authorized if needed.
So if the numbers are still visible, does that mean it was never decked?
If the engine still has stock bores, I highly doubt someone pulled it apart and didn't have it bored out but had it decked. Just seems rather unlikely. Secondly, someone going through that effort wouldn't be likely to put a DOD cam back in it, as their failures are well documented. I still am REALLY confused how any reputable machine shop doesn't know how to look up the stock deck height on an LS and then measure it. Blocks vary from GM, but they're nominally 9.240" I couldn't tell you if numbers being visible means anything. How deep are the numbers? .010? If the deck had a clean up pass of .005, it would still be visible, correct? So that's not an indicator. Measuring the block is an indicator, and I would still say run from any shop that tells you they don't know how to figure it out. If you still want to do this, use it as a learning experience, but I will tell you that if you're unable to use/read precision measuring equipment, you're going to be over your head building an engine. You can fudge it with plastigauge, certainly, but it's far from accurate. I'd suggest finding a friend who knows a bit more, and double and triple checking every step of the process. Come on here with questions, there are tons of people who know far more than me who will be ready to answer you. Hell, I ask questions on here all the time about everything, and I get great feedback. Good luck, it's not impossible to do this if you're meticulous about it.
Ok that makes sense on the numbers. I’m pretty good with the measuring tools and was getting better. Yes that would be nice if i knew someone that could help me out. I have another car to use while doing this. I’m mechanically inclined 20years line tech. Just never rebuilt motors they quit doing that when i started. The dealerships quit rebuilding anything really. When i was in high school i was bussed downtown phx and we rebuilt starters, alternators and such but never had to when i got to the dealer a tech later.
I’m still pretty excited to build this motor and run it! Yes learning experience and I’m not in a hurry but dont have 3 or more months maybe longer for machine work. So i’m waiting to hear back on results. Bore taper and such. Because i checked them before to be ok. So either I'm wrong or they are just ?? Got to trust somewhat until i’m more experienced.
Can you point me to a website or videos or ?? As to the way a machine shop or anyone how to check deck height and if the block is junk. I only found stuff on if the engine is built and you check with bridge micrometer? But the block is bare!
I always assumed the machine shops know the procedure and measurements block loaded or bare. Maybe he does, will see.
So on another note, he said dont buy new rods not needed. So they are not trying to sell me rods. But i thought these parts are only good for a 100k but 200k mikes? I know engines go way past that but I was wanting to put all new parts so i would be assured another 200k.
He said the rods are fine. ??
I already picked up new GM stock crankshaft, camshaft and other stuff a while ago. Got a good deal in them. Just recently purchased the pistons and rods and was able to return them. I could have kept them and used them but was worried i would need oversized pistons now, so i sent them back while i still could. So I'm into this pretty deep.
The Gen IV rods are extremely strong, like 1500 horsepower capable, so he's right - you don't need rods, or new rod bolts. Use them as is. And I'm saying they're capable of 1500 HP AFTER 200K miles. You prob didn't need a new crank, but may as well use what you bought. I put a used stock crankshaft in the engine I'm building now, and it's going to be close to 1000 HP at the crank. No worries, and it ( the crank ) has close to 200K on it. As for measuring the deck height, it's straightforward, but to do the actual measurement requires calculations. Most machine shops have fixtures to make measuring easy, which is why I find it odd that this shop you went to says they can't do it. Check this page out: https://www.k1technologies.com/k1-bl...what-it-means/
Last edited by LS1Formulation; 03-15-2024 at 10:23 PM.
1st Off, No LS block I have ever messed with was perfectly flat...
2nd On these engines the pistons are typically above the deck at TDC. So you on a standard bore, you need to know how much they are out of the hole to determine the proper gasket thickness.
When you over bore, this is less of an issue because the over sized pistons will have a smaller compression height to compensate for the compression ratio on the larger piston.
We can not see or measure your current engine so we can tell you what direction to go. Where are you located? Perhaps someone can recommend someone in your area.
Here is a few videos showing the LS block surface as its being machined so you can see what I am referring to.
Thank you for the reply’s
i just watch those same videos last night.
Well at this point they’re in the current machine shop hands.
I will post as soon as I hear back from them.
I now have a better understanding of this.
This has been a great learning experience. I had no idea it was such a complex operation to rebuild an engine. I have a new respect for this now. if I get this one running again I will feel pretty darn good!
Picked up from machine shop today! Big language barrier. They seemed nice but not sure i understood everything.
Heads valve job, installed new stock melling valves, beehive .550 springs, retainers and keepers.
Told me it took .0012 (12 thousands)to get heads flat.
Block decked and bored over .20 and honed.
I asked if stock headgaskets will still work. He said yes. I dont know how much milling it took to get flat.
He said block and heads are in great shape now.
He transfered the new oversized enginetech .50 pistons to my stock rods. Handed me a new set of enginetech .50 ring set.
I asked if the ring gap is pre set. He said yes if daily driver no performance upgrades done.
The block and heads do look real good!
I asked if the new stock pushrods 7.400 will still work.
I’m not sure what he said. So i guess i need to by a pushrod checker.
I have to set the rockers torque to spec. Never done that but should not be to tuff. Ive done more complicated before.
I guess i have to install everything and then check ptv clearance. Since I don’t know deck height.
Yes it would be nice if I had an exp person here local to just guide me but nope. So i got to wing it.
Oh and theres a new plug in both heads. I’m assuming they are overheat plugs for warranty. O wait I have a warranty. Lol.
Here is the dowel I was referring too. It looks like it might have been milled over. This is supposed to be proud of the block and they are removable. I am not sure what's going But I can tell you its not correct. You will need the Locating Sleeves to keep the head centered.
I believe the correct part number should be GM #12570326. BTR has the same thing at a fraction of the price under BTR70326
There should be 1 at each lower corner of the block on all 4 corners.
As for the Cylinder head and the core plugs. Here is the Info to help you and the machine shop out. I am sure they will make right for you.
GM 11562126 => Dims. 1.261in. Dia X 0.310in. Ht X 0.050in. Thk - Matl.-SS304
So it's probably supposed to be a 32MM not 1-1/4
Last edited by 1FastBrick; 03-27-2024 at 12:17 AM.
I am totally bewildered! I took all the dowel pins out and ordered new before dropping off at machine shop. I would have never been able to sand the block originally if the dowel pin was in there. When i picked up the block from the machine shop they handed me 3 dowel pins. I was like they’re not mine? He had a look on his face like i was crazy. He said something in broken english that i have no idea what he said. Geez! Why would they need to put a pin in?
I didn't see that cut dowel pin when i looked at the block there. If I had more experience I’m sure i would have. I would have caught it when i went to install new.
So i dont want to go back there! Eek!
And i have no idea what other machine shop is reputable around here. The shop we used 20years ago closed during covid.
I was refered to this machine shop by another auto repair shop. They have good reviews except a few non related to work done, bad reviews, like hard to find the shop, no signs. I think they just relocated there recently.
Should not be to tough to remove and replace those plugs my self right?
How do i get that dowel pin out? Should be fun!
Yes it’s my block and heads. I marked them with my name and initials.
Cant quite tell from the first pic with the engine on the engine stand if the same as after milled but
I honestly dont remember there being a dowel there or not. I know for sure there was no dowel sticking out when i sanded the block stopped and took to machine shop. It would have torn my sandpaper and would have never slid back and forth. So idk.
I am totally bewildered! I took all the dowel pins out and ordered new before dropping off at machine shop. I would have never been able to sand the block originally if the dowel pin was in there. When i picked up the block from the machine shop they handed me 3 dowel pins. I was like they’re not mine? He had a look on his face like i was crazy. He said something in broken english that i have no idea what he said. Geez! Why would they need to put a pin in?
I didn't see that cut dowel pin when i looked at the block there. If I had more experience I’m sure i would have. I would have caught it when i went to install new.
So i dont want to go back there! Eek!
And i have no idea what other machine shop is reputable around here. The shop we used 20years ago closed during covid.
I was refered to this machine shop by another auto repair shop. They have good reviews except a few non related to work done, bad reviews, like hard to find the shop, no signs. I think they just relocated there recently.
Should not be to tough to remove and replace those plugs my self right?
How do i get that dowel pin out? Should be fun!
Yes i’m going to clean everything multiple times!
Thank you for the help!
Bill, you never mentioned where you located.
The dowel should not be too hard to remove. I just don't know what you have access to. Maybe work at it with a 90 degree pick from the ID of the Diameter.
There is a few ways to do the plugs. One is a body slide hammer. They also sell a little puller tool. The other is with a screwdriver and a hammer.
Here is the too they sell.
Here is how to knock one inward and pry it out method. Just be careful as you can easily mar up the aluminum and damage the opening.
Ok Good news! After I got home from work and inspected the block, it’s ok, theres no dowel milled over or in that hole. The picture I took made it look like it was milled over. Wow! I couldn't believe it!
When you showed that pic with the arrow and i remembered them trying to give me those dowels i was like no way how could they do that!
I was like, i inspected the block and heads??
Crazy how a picture can show a different look!
I purchased the GM plugs and will swap those out.
I still have no idea how much they milled off the block but they said the stock head gaskets will be fine.
Ive been busy at work and can only work on this a couple hours a week. I will watch those videos and read up on how to measure and be sure the gasket will seal.
I live in Las Vegas by the way.
Thanks again for the help!
Bill, that's excellent news!!!
That picture sure looks deciveing.
So on the heads, typically they only put a heat tag on one side. If you can read the label on one of the plugs and it says 1-1/4, then I would change them.
As for the head gaskets, you will likely be fine. Once you get the short block assembled, you can check the piston protrusion. So far I have been good on every block I have had decked.
03-14-2024, 12:04 PM
Engine rebuild gone wrong! 
