I am looking to Turbocharge my 98 Tahoe, How should I prepare my engine, what mods do I need/would be recommended.

[DonYukon]

What is stretching anything on a high mileage motor? The rings are already gapped for boost. Why would a seasoned motor be weaker than a new one? I did the blower at 240k on my 1500.

i mean you're not wrong but 5-600 horsepower seems like a lot on a power and drivetrain that was meant for sub 300 hp. Just my 02 cents is all. If I'm honest I've never built anything with 380+ wheel HP and I had some issues with said vehicle (non 400) I'm no expert in this department but im assuming im spewing common sense which I may lack

 

[Supercharged111]

i mean you're not wrong but 5-600 horsepower seems like a lot on a power and drivetrain that was meant for sub 300 hp. Just my 02 cents is all. If I'm honest I've never built anything with 380+ wheel HP and I had some issues with said vehicle (non 400) I'm no expert in this department but im assuming im spewing common sense which I may lack

The thing is there's not a ton of info out there on folks shooting for the moon. I'll say 450-500 wheel, more the 450 mark, seems to be a generally accepted limit for the LT1, but that's NA and spinning in the 6000-7000 range. A boosted L31 will likely live at or under 6000. With a safe tune, the pistons aren't in any danger, so why would 100k+ miles make it prone to failure? I think that's a very old school way of thinking.

 

[yevgenievich]

High boost and cast pistons often don't mix. Rods and rod bolts would be next. And rings are wore to live better for boost by higher miles, but lower boost levels and conservative tune recommended.

 

[DonYukon]

The thing is there's not a ton of info out there on folks shooting for the moon. I'll say 450-500 wheel, more the 450 mark, seems to be a generally accepted limit for the LT1, but that's NA and spinning in the 6000-7000 range. A boosted L31 will likely live at or under 6000. With a safe tune, the pistons aren't in any danger, so why would 100k+ miles make it prone to failure? I think that's a very old school way of thinking.

Well While it may be old school it is backed by science. engines have planned obsolescence. they will ultimately fail depending on use over time. that time is obviously shorter if the parameters of its design is compromised. correct me if I'm wrong but the L31 if I remember correctly are all Cast with no Forged internals while (maybe wrong here) the Lt1 has some kind of cooling difference and some forged rods or something. One was built to be in a Vette to go fast and the other for reliability sake. Forged internals as we know handle boost and general high output demands better than that of cast components. All I'm stating is that a motor that already has wear and tear on it will only put further stress on it and cause issues without digging into it and rebuilding it. and maybe i should have said something more along the lines of 150-200K miles knowing these engines but still.

My whole point is these L31s were meant more for work horses and to be operated within a set HP figure for reliability. any major change to that and you will run the risk of blowing it up. I.E ask anyone on here how 35+ inch tires and offroading goes with the factory 10 bolt or CV axles. they work great with the stock tire but will be prone to failure with any use of the skinny pedal after throwing more unsprung weight at it.

 

[Supercharged111]

L31 has hypereutectic pistons and a nodular iron crank with powdered metal rods if I'm remembering correctly. My point is what exactly becomes more prone to failure with miles? Why is a high mileage L31 more prone to failure than a fresh one? Stock for stock of course. You may end up with a bunch of blowby, but is that a death sentence? If the bearings are shot it doesn't matter if it's NA, boosted, or whatever junk is junk.

 

[stutaeng]

Looks like the internet says 500-600 HP is the limit for this engine, but I'm no engine builder expert.

I do agree on the "worn" engine already having gapped piston rings, so really no reason to open it up. I would have thought at 500-600 HP you would have to worry about the 2-bolt vs 4-bolt crank, but then there's folks that say that doesn't really matter. I would think it does at that level, and probably either would be the weak point? I'm just guessing here though.

I'm pretty sure OP has a 2-bolt main block from the factory.

 

[Supercharged111]

Looks like the internet says 500-600 HP is the limit for this engine, but I'm no engine builder expert.

I do agree on the "worn" engine already having gapped piston rings, so really no reason to open it up. I would have thought at 500-600 HP you would have to worry about the 2-bolt vs 4-bolt crank, but then there's folks that say that doesn't really matter. I would think it does at that level, and probably either would be the weak point? I'm just guessing here though.

I'm pretty sure OP has a 2-bolt main block from the factory.

I think the 2 bolt vs 4 bolt is more of a concern with RPM than it is boost.

 

[Erik the Awful]

If you're going to have the engine out, I'd take the time to open up the rings. Trusting mileage to open them up for you isn't the wisest idea.

Lowered compression is good.

Personally, I'm not a fan of forced induction without an intercooler. Heat is the greatest enemy of boost.

 

[mountie]

When I had my '88 C2500 / 350cid replaced at 220,000, the race shop suggested a crate 350 Vortec 4-bolt main. We decided on an 8 1/2 - to 1 compression. I was going to add a ProCharger for a little bit more power. I never got around to installing it. ( Boy, that engine ran great on regular gas!)
I also had an Art Carr transmission built that could handle 650 hp. ( 700R4 )

But.... pumping a ton of horse power to a stock truck? You will have to build everything to handle it!!

 

[1989GMCSIERRA]

Without any compromises (no removal of A/C or Power steering ect.) I want to install a turbo. I have the whole system planned out (not bought) with few kinks left to deal with, my question remains; What next? First and foremost I am already planning on swapping the PCM with a 0411, the support for tuning for boost and other applications make it the clear choice for this. But other than that I'm not sure everything is ready. Are there timing changes I should make? Should I get a forged crank or cam shaft? New pistons and Rods? Or is the 350 small block ready to handle 500-600 Horsies? Maybe something not even remotely on this list! I want to ask all you smarter guys before I potentially hurt my perfectly good car. Any other tips would be appreciated as well.

Your trans is gonna crap the bed even if your block can withstand 5-600 Ho.
You can make 5/600 but that stock motor isn’t gonna stay alive long enough.
Assuming you are gonna rebuild it….forged internals. I would keep the compression stock or lower it for longevity. With a turbo car you are gonna want to leave it idling a bit once you stop. Remember that turbo is spinning at ten thousand rpm or more. You’ll need to give it time to cool down. More frequent oil changes also. Not sure if this is a problem anymore but the oil feed and drain lines used to build up deposits. It was called coking. Maybe the made feed and drain lines bigger.