Theoretical LS build, walk with me.

I have a 2007 Silverado with a 5.3 that has a bit over 160k miles on it. I bought it new. I don't really like it but it's good at being a truck and a decree has been passed that I will keep it until we leave Texas.
That has me thinking, at some point in the future I may find myself needing to do a motor refresh/replacement of some sort. Who wants to put a stock 5.3 back in? Not this guy.
Let's say....500 hp, retains all of the stock accessories, naturally aspirated, can still tow a car trailer, passes emissions. I understand that this motor would blow up the transmission and rear end, so those would need to be addressed.

So how would I go about this?

mazdeuce wrote: That has me thinking, at some point in the future I may find myself needing to do a motor refresh/replacement of some sort.

You're going to be waiting a very long time.

When the oil pressure disappears in 40-50k miles, drop the oil pan and replace the pickup tube O-ring that has shrunk/disappeared. Use a NEW oil pan gasket since the old one is probably blown out at the oil passages. Ta-da, engine is good for another 200k. Then replace the pan gasket and O-ring again and keep going.

Freaking anvils, these engines are.

If you want more power, go for more power when it is convenient for you. Don't wait for the engine to want out, it's a highly understressed engine that has been very well engineered.

To directly address your question, towing + naturally aspirated power = displacement. Period. As a bonus it should have no problem passing emissions. Replace the shortblock with the most displacement you can find. 421, 427, 454ci bottom end. Keep cam mild for the displacement (and with a broad lobe center) and compression sane, you want an engine that is happy living at heavy power, so you don't want a 13:1 monster.

Personally? I'd bolt in an 8100 and be done with it.

If your staying stockish bottom end, 500 probably wont be very good at being a truck.

Gotta stay pretty small on cam to work with stock converter. Who wants a big loose converter for towing and doing truck things. Ls6 cam with 243/799s off a later 5.3, tbss intake, with accompanying bolt ons is the cheap and easy way to 450 with pretty stock driveability. Spend a little more money for a custom cam, some porting on the heads or aftermarket castings, and an lsxrt intake and you might be at 500 crank.

Now if you move to a big bore motor like the 6.0 you can slap gm l92 heads on, then 500hp is easy, even with good driveability, plus you can run more cam with the bigger displacement.

We did a LQ4 6.0 for a buddies 1500hd. He has 243s with no additional work, small texas speed cam (211/218 iirc), Fast LSXrt 102 mm intake and longtubes.

Made like 366whp through a 4l80e and a 14 bolt. So definitely not 500, but it drives great, and is quick for a big ass truck

500 hp will need some 243 heads fully ported. Not cheap. Cam in the 234/244 range. 11:1 is pretty easy to use with 91 octane. Stock intake will support 500, but a fuel system overhaul will be needed; pump, injectors, fuel rail.

But it will be a lumpy-idle hot rod engine.

Other idea would be to get the LQ9 heads (same ports and flow as the stock LS6 head, but bigger chambers) and then give it 10 psi

And neither will be smog legal unless they just do a visual and have selective sight.

We don't have visual smog, I just need to be able to plug in the computer and have it say that all is good. Well, I suppose I need cats and what not, but the visual side is pretty loose.
I'm not stuck with 5.3 block. Spending money for more cubic inches is theoretically fine, since this is theoretical and all.
This is very much a "I should start collecting parts, just because" type of exercise. The easy but $$$ button would be to just order up an LS7 crate motor, but it seems like maybe there is more power to be had for the money or less money to be spent for the power.
Transmission would need to be dealt with so let's assume I build it to work.

My gut feeling is you wouldn't want an LS7 per se, compression is probably too high for truck duty. There's a big difference between accelerating a Corvette and pulling 11,000lb of truck and trailer up a grade.

More displacement, less compression, don't really want to go crazy with cam either.

Ok, but starting with an LS7 block and bottom end, maybe heads? Different pistons for lower CR. Milder cam, move the torque curve down? Something like that?

No. Start with LS2 block($1200 new) and cnc'ed ls3 heads(same). Pick up a used crank and rods, have them balanced to new pistons, toss on an L92 truck intake and sneeze pretty much any decent cam into it for 500+ unstressed horsepowers. Wave goodbye to your trans shortly thereafter and then your rear axle sometime shortly after you pay out the noze for a stout transmission.

There is no replacement for displacement. For a given hp, more displacement will make more torque and at a lower RPM.

What if you started with an 8100?

curtis73 wrote: There is no replacement for displacement. For a given hp, more displacement will make more torque and at a lower RPM. What if you started with an 8100?

The 8100/Allison is a great combo, and if I were building an older truck with a modern powerplant that's the route I'd take.
But my truck already has AC and traction control and all of the neat integrated features that make it a fairly nice modern truck, and I'd love to keep them. A different LS seems to be the easy button to keeping all of that with more power.

patgizz wrote: No. Start with LS2 block($1200 new) and cnc'ed ls3 heads(same). Pick up a used crank and rods, have them balanced to new pistons, toss on an L92 truck intake and sneeze pretty much any decent cam into it for 500+ unstressed horsepowers. Wave goodbye to your trans shortly thereafter and then your rear axle sometime shortly after you pay out the noze for a stout transmission.

Thanks for that recipe. Sounds easy enough.
And yes, I know more power requires a new transmission/rear end.

Stock 5.3 replacement, booost. Bam, 600rwhp with a Bob Costas turbo and cheapass ls9 camshaft. Just make sure you swap out the valve springs with something like PAC 1218's.

You'll still be in under 4K with a replacement jy 5.3.

Boosted stock LS long block doesn't seem like a long living combo when a trailer is involved. That being said I'm seriously considering selling my Cummins truck, getting a 2wd GMT800 and doing something that's probably pretty close to what Mazdeuce is thinking here

Also, 100% of my LS knowledge beyond driving stock 5.3s is theoretical.

Oh and one more thought, does anybody make stuff to beef up a 6L80E on the cheap yet?

mazdeuce wrote:

curtis73 wrote: There is no replacement for displacement. For a given hp, more displacement will make more torque and at a lower RPM. What if you started with an 8100?

The 8100/Allison is a great combo, and if I were building an older truck with a modern powerplant that's the route I'd take. But my truck already has AC and traction control and all of the neat integrated features that make it a fairly nice modern truck, and I'd love to keep them. A different LS seems to be the easy button to keeping all of that with more power.

That is the beauty of the 8100. It more or less uses the same computer setup as a Gen III. Keeping everything electronically happy should be a non-issue. Maybe have to change the throttle pedal, maybe not, kinda doubt it. Computer speaks the same CAN language.

I forget now where the 8100 puts the A/C compressor. But even if it's in a different spot, it's not like you'd be doing a cross-chassis swap, it should all be bolt-up-able with OE parts, no hackjob.

Mind you, I can totally respect wanting to keep the engine family you already have, and if there's one to keep, this is a good one. But when you say 500hp and you want to tow with it, my mind goes for grabbing the most displacement you can.

At the very least, you'd need to ditch the 5.3 for a 6.0 or larger.

I have driven an 8100-engined C2500 (yes, a 2wd!) and it was disturbingly fast for a beat-up old work truck. Not crazy fast, but it gave the sensation that it didn't really care if the bed was empty or heaping with gravel. Not like any 4.8-6.0 engined truck i'd ever driven. When the trans shifted, the truck accelerated to meet the engine's speed, not the other way around.

In reply to Knurled:

The 8100 is heavy. Not kind of heavy, really heavy. The Allison might be the best part of the combo and my understanding is that the Allison doesn't fit under the 1/2 ton trucks. Also, adding that much weight and beefing up the suspension is leading me toward building a medium duty truck, and I quite like my half ton in compsrison to the big trucks. I'd love an 8100 C/K Blazer though.
A friend with a 2wd 8100 truck just sold his. I enjoyed accelerating in it, but hated pretty much everything else about it. Fantastic motor/trans in an otherwise crappy truck.

Fair enough I will allow that there's a whole lotta metal in the Mark VI. It's not quite the hoist-bender that a Duramax is (allegedly it's right on 1000lb!) but it's a good deal more than an LQ4.

You can, at least, get over 7 liters with your existing architecture. Forced induction and towing sort of gives me the heebie-jeebies with respect to thermal management. I know Ford's doing the hell out of it right now, but they have also spent just a little bit of time engineering that package to work that way.

400hp NA on a 5.3 is easy (cam and a tune, some stock cams will even get you there), that last 100 is going to cost you as mentioned above. With boost OTOH I'm not entirely sure you even need to open the motor to make 500, probably a good idea to gap the rings though.

In reply to Knurled:

my thinking as well. I know of more than a few with close to 400k bone stock and original. They all have CSK but have had it for 300k miles. Dad's 03 5.3 doesn't even use a half quart of oil in 5k mile OCI's with 230k on it.

Bobzilla wrote: In reply to Knurled: my thinking as well. I know of more than a few with close to 400k bone stock and original. They all have CSK but have had it for 300k miles. Dad's 03 5.3 doesn't even use a half quart of oil in 5k mile OCI's with 230k on it.

I just pumped 150 shot of nitrous through a questionable mileage 5.3. It sounded glorious.

I'm pretty sure I'm going the 5.3/ls6 heads combo for my next cheapo build. I am almost tempted to pull the lq4 and 4l80e from my work van into my impala instead of putting it back on the road and i'm thinking my belair might donate it's vortec head 330hp 355 to something else and get a turbo 5.3.

One of the guys I work with told me he threw threw a 200 shot at a ported head LS6 cam'd 5.3 in his GMC. Based on the cloud of smoke I saw when he started it up to leave earlier today, I believe him.

A pair of turbos will deal with both the now and the future. Boost it till it blows, then build it till it don't.

To tag along here how easy is it to diy tune these for a little more kick?