Any LSx Experts in the house?

"Snuze: Needs another Swede" (markg)
07/07/2015 at 12:26 • Filed to: None

This weekend Dad and I were debating a motor for his project truck. He wants 500HP (at the crank) all motor, no power adders. He thinks we can upgrade the existing engine, which is an L31, a 265HP 350 V8. It’s got Vortec iron heads and not much else going for it. Also uses a funky fuel spider with non-upgradable 19# injectors, so the entire top end has to be redone.

I’m pushing for an LS swap. I’ve seen some amazing stuff with the LY6 - it’s the 6.0L V8 out of the newer Silverados, Suburbans, etc. Its an iron block with LS3 aluminum heads and in-block VVT. It also makes 385HP bone stock and they are available for around $2000-2500 with ecu, harness, and accessories. Mast Motorsport makes a VVT-HO Cam kit that, with an LS3 intake swap and headers, puts down 420-430RWHP, which back converts to about 500HP at the crank.

So what say you? Keep the old iron or go high-tech?

DISCUSSION (21)

64Mali > Snuze: Needs another Swede
07/07/2015 at 12:33

If he wants 500 HP. Go LS 6.0. I also hate the spider on the L31 after having to replace it in my burban.

Snuze: Needs another Swede > 64Mali
07/07/2015 at 12:35

Yeah, I did some really back of the napkin pricing and I think honestly it would be extremely close as far as which setup costs more. The LS swap obviously is more up front because you’re dropping $2k on a motor, but you can sink a lot into a 350 to make what the LY6 does stock.

DoYouEvenShift > Snuze: Needs another Swede
07/07/2015 at 12:39

http://www.hotrod.com/how-to/engine/…

If you can get an LY6, you should have a solid start. A nice VVT cam will get you pretty far. Ditch the afm, use a thinner headgasket, maybe mill the heads. Compression is pretty low stock, 9.6 I think, so getting it around 10.5 should net you a pretty good gain by itself, and will help with the cam as well.

Sweet Trav > Snuze: Needs another Swede
07/07/2015 at 12:40

500 hp is only half the battle, how much low speed torque does he want to get his thing moving?

You can build a 383 stroker and carb it to make the power, or a 406 SBC. If you go with an LS truck swap, find a wrecked Escalade, that would be the best place to start, you will want to pull the whole drivetrain and front accessories. It already has good heads, have those ported and polished, bump up the compression with some good forged pistons, get an aftermarket intake and healthy cam. Torque is far more importan that horsepower when getting something as heavy as a truck moving. I’d rather have 550 ft/lbs of torque and 450 hp than the other way around.

Also for trucks... dont forget the old Gen IV big block. An 8.1 vortec can be built well.

Snuze: Needs another Swede > Sweet Trav
07/07/2015 at 12:50

Psh! Rednecks don’t think about stuff like that. We pick a power number (the bigger the better) and build to it as cheaply as possible, conserving the rest of our money for beer.

In all seriousness, though, anything will be better than what it has. The L31 puts down about 325 ft-lbs bone stock. The stock LY6 will make 400ft-lbs and the Mast VVT cam should at least maintain that if not make more. That’s another reason I’m really in favor of going to that motor.

We’ve talked about doing a 383 or 406, but my dad doesn’t want to run a carb in it. The truck is a 97 so it still has to go through emissions in lovely Maryland. Another think I like about the LY6 is it’s basically the Escalade motor (L92) but with an iron block. It’s the exact same cylinder heads, just less cam and lower compression. It’s a bit cheaper, and I’m trying to convince him to throw some boost on it down the road (single 78mm turbo setup) so the iron block would be a better choice in the long run.

I’d love to do a big block but I don’t know shit about them. Also not sure what kind of cost is involved or what the weight penalty is.

scubaduba > Snuze: Needs another Swede
07/07/2015 at 12:52

IMOP Best budget deal would be 5.3L, L33 would be best 100 lbs lighter and heads made for LS6 along with higher compression 9.9-1. Longtubes, Decent Cam/springs/pushrods, Try and pickup a LS6 intake and injectors and you should be in the 400+ range you could mill the heads a thousands if you are never going to boost it and get closer to 500hp.

Snuze: Needs another Swede > DoYouEvenShift
07/07/2015 at 12:56

Thanks, I’ll have to bookmark that article. Sounds very similar to my approach.

Snuze: Needs another Swede > scubaduba
07/07/2015 at 13:01

Hmm, that’s a good idea. I’d briefly considered the 5.3L engines but kind of written them off. I’ll have to bring that up to Dad.

Sweet Trav > Snuze: Needs another Swede
07/07/2015 at 13:26

biggest problem with 5.3l's are is they do not accept most aftermarket heads as the bores are too small. you can make 450 pretty easy on them though, however the cubes and stroke of the 6.0/6.2 may benefit a full size truck.

Snuze: Needs another Swede > Sweet Trav
07/07/2015 at 13:31

Yeah, I was aware of the small bore. Part of the reason I’d written them off was that lack of potential. But if he really wants to keep things cheap, which seemed to be his reasoning for keeping the 350, it could be a viable option. But I think you’re right, a truck would benefit a lot from the bigger bore 6.0 or 6.2.

Manwich - now Keto-Friendly > Snuze: Needs another Swede
07/07/2015 at 14:04

Going from 265 to 500 hp would make me concerned about the transmission and other things. I think what Travis said of getting a wrecked Cadillac Escalade and using the drivetrain from that would be the best way to go.

Manwich - now Keto-Friendly > Snuze: Needs another Swede
07/07/2015 at 14:11

“In all seriousness, though, anything will be better than what it has.”

Not true. You could swap in the 4.3L L99 V8 that was in the Chevy Caprice for a few years in the 1990s... and it would definitely be worse:

https://en.wikipedia.org/wiki/GM_small-…

And the only thing worse than that would be trying to work with an old 262 CID version of the SBC from the 1970s...

https://en.wikipedia.org/wiki/Chevrolet…

Sweet Trav > Snuze: Needs another Swede
07/07/2015 at 14:17

Or you could try a new MPFI intake on the vortec and turbo it until it blows up?

Snuze: Needs another Swede > Manwich - now Keto-Friendly
07/07/2015 at 15:28

It’s got a 4L60E in it at the moment. The stock trans is probably good to 350HP or something like that. A built 4L60 is good for right about 500HP, depending on weight, tires, converter, etc. We’re planning to just go to a 4L80E - they can hold way more power and also have a more even ratios spread.

Snuze: Needs another Swede > Manwich - now Keto-Friendly
07/07/2015 at 15:36

Haha, I’m aware that there are a lot of worse options. I’m surprised you missed the 305 or the reviled 307.

But that would require us actively seeking a poor solution. Pretty much any LS, or anything we do to upgrade the L31 would be better. Case and point, my dad had a GMC Savanna 3500 cargo van also powered by an L31 for his work truck. He replaced it about a year ago with a Chevrolet Express 2500 with the L20 4.8L V8, which makes 285HP, 295ft-lbs, so 20HP more than the L31, although it makes about 30ft-lbs less torque. But it’s got a 6 speed transmission behind it, which makes up for the lack of torque, and it’s pulling 15-17 MPG all day long. On an exceptional day the old L31 van got 13 MPG.

Snuze: Needs another Swede > Sweet Trav
07/07/2015 at 16:02

I am pushing for a turbo, eventually. I tried that same line of reasoning, turbo the L31 to within an inch of it’s life, just for LOLZ, but somehow he’s not a fan. He wants it all motor for the time being.

But, part of my reasoning for the LY6 was that it’s an iron block and has relatively low compression - 9.6:1, so it’s essentially turbo ready. I know my dad well enough to know that, eventually he will get bored and want to tinker. I think that’s kind of why he’s interested in fooling with the 350, just because he can. I’m just trying to show him it’s a wash in terms of cost so why not just skip to the LS.

Even though 500HP is probably plenty for the street, I think he will eventually want more. And I want to build a stupid turbo LS motor because why not? So when we reach that point, we can go back to the iron manifolds but flipped 180 degrees to point forward. Then fab up a Y-pipe, mount an 80mm turbo, and throw in some bigger injectors. Boom! With intercooling and a tune we should be able to run about 10psi safely, which I think will get us to around 750HP. Or, if I have my way, new rods and pistons, an LS9 cam, and shoot for 1000HP because how many people can say they have 1000HP?

Sweet Trav > Snuze: Needs another Swede
07/07/2015 at 17:03

Except a 4lL60e for a gen 1 isn’t the same as for an LS motor, skip the 4l60 all together and build a 4l80e

Manwich - now Keto-Friendly > Snuze: Needs another Swede
07/07/2015 at 18:50

I knew about the 305... but I didn’t mention it was it wasn’t as much of an oddball and has decent non-performance support. But I did miss the 307 which I normally associate with Oldsmobile, not Chevy.

scubaduba > Snuze: Needs another Swede
07/07/2015 at 19:28

All depends on where you want to end up. Just looking for4-500hp the L33 5.3 would be great as you are running an aluminium block and heads(that were origionally devopled for the LS6 so aftermarket heads are if you are looking for all out performance. As far as lack of potential I disagree. Stock 5.3’s can make 600-900+ hp Boosted with stock bottom end, obviously the fuse is shorter the more boost that is ran... But there are many budget built 383 iron block 5.3’s running 600+hp boosted. Really just comes down to where you want to end up at once the project is done. If you are looking for towing power and maybe even more than 500hp down the road hands down a 6.0L iron block as Travis is saying. There are more options as far as aftermarkets. You will also want to make sure you get a fly by cable setup rather than fly by wire, otherwise you will need to buy a pedal and few more things to get everything working correctly.

Snuze: Needs another Swede > Sweet Trav
07/07/2015 at 21:39

Yeah, we were already planning to go to the 4L80.

Snuze: Needs another Swede > Manwich - now Keto-Friendly
07/07/2015 at 21:45

True, the 305 was a decent motor for non performance applications, but pretty bad for performance use.

Another favorite was the L83 Crossfire V8 from the Corvette, pumping out a whopping 205HP. Although it was slightly better than the L81 from a couple years earlier making an all time low 190HP.