I have a 2001 Silverado 5.3L with 168K on the clock. I took my tuck to the repair shop for what sounded like a vibration noise at idle, and my fears were confirmed. They believe that there is a worn main bearing or rod bearing on my LM7. They don't want to dig into the engine at this time because they don't want to break something else or open a pandora's box of troubles. They said it should be fine for now but I still want to get a second opinion. I have been wanting to build an engine for the truck, but this just pushes up my time frame , so I am shooting for next fall to do the swap. Should I be ok until then? I drive 500-750 miles a month, but come May/june I plan to pick up a new DD, then the truck will sit most of the time.

This leads me into my next question, I am looking to either build an engine or get a long block from one of the sponsors. But I want to know if I am going down the right path. I am looking for 450-550 hp, as I feel that is what my stock intake, fuel pump and etc can support, I realize I will need a new trans and injectors. Possibly a rear end.
My 3 choices are as follows:
Buy a Stock bottom end LQ9, with modified heads and etc. :this would be the cheapest, and would give me the option to further modify the engine down the road if i wanted to. Basically I would want some heads I could use for a later project, but don't know if this is realistic. I am concerned the Cam might need to be larger then I am comfortable with. ($3500-$5000)

Buy a 408 Long block. Pretty pricey and may be overkill for my application and use. ($7000+)

Buy a finished LQ9 block from a large retailer ($750) , buy a 408 stroker assembly from a sponsor ($1800-2200), then I would look at AFR 230 heads or TFS heads ($2000-2500) cam kit ($800) and misc ($500) ($6000+)

As I said I want 450-550 hp, I need the truck to function as a truck and even though I probably won't keep it another 100K, i'd like the engine to last at least 100K. I am concerned about the idle characteristics, I don't want it too rough.


Cliff notes:
1: will a worn main or Rod bearing last for another 10K miles
2: right avenue for my application
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This is a hard question to answer, it depends how bad it is and how the vehicle is used etc. Assuming it is a rod bearing that is the issue, it could last a week or 6 months, but 10k miles is a crapshoot, it may it may not last, there is no real way to give a accurate answer on that, but I would start saving up for the new engine now.

As far as what direction you should go for your new engine it really depends on what you are comfortable doing and what your plans are for the truck. If it was my truck I would be looking into used LQ9s and building it myself, but if you are not comfortable with the work then look into buying a new shortblock or longblock from one of the sponsors. Thompson Motorsports, Texas Seed both have tons of short and long block options that cover most applications. I know its a big decision but look at it from this standpoint, How much money do you have to spend, that should be the first thing, then see what your options are with the money you have, and then go from there.

 

"They don't want to dig into the engine at this time because they don't want to break something else or open a pandora's box of troubles"

Huh???

 

I have taken videos, the noise is a low "WOP WOP WOP WOP" it is more pronounced under the engine, but the fan wash overpowers the microphone.
Engine Bay
Under the truck

I have some major expenses to get past in the near term, so I'm trying to buy time to get past them.

Basically I am looking at the two you mentioned and what engine I decide on will ultimately decide which one I go with. As I mentioned I am looking for 450-550 (engine) HP, I want the engine to last at least 100K miles and not bee so rough at idle it knocks my fillings out. The truck will become a secondary project vehicle and mainly just be used as backup and for "truck stuff". I'd love a 408, because if I'm going to do the swap, might as well go big, but it is a little more than I want to spend, I question the longevity and it is probably more than I need. I keep the truck for a long time I would probably put a turbo on it when my son gets older as a project and I would need to pull the rotating assembly to install a lower compression ratio anyways. I think a stock LQ9 shortblock with upgraded heads/cam would give me the power I want now, plus I could always put a stroker assembly in it later and could go turbo at that time, but that is all an additional cost at a later time.

I'm comfortable with assembling an engine, I just don't know if I have the time/patience to really do all the precise short block assembly stuff (plastigauge the bearings, fitting of rings, and etc.) I think building from a shortblock would be more entertaining.


Basically I don't think they wanted to tear in the engine, spend a $1000+ pinpointing the issue, just to have to end up throwing in a new motor.

 

Option T...

Pick up a bonestock 4.8/5.3 and throw a turbo on it. Twice the fun, half the cost of your first/cheapest option. Will easily make the power you want and more.

 

turbo might be down the road, but I want to save that project for when my son gets a little older.