TBI vs LS replacement

[Kudzu]

I have a near mint 93 Suburban and it's time for a engine, I hear a rob knock on startup. My Suburban is a driver, I use it around town and we take it on road trips. Very seldom tow any more than a small trailer with a load of lumber or a lawnmower. When I get my wood boat I am restoring I will be towing it on short trips to the lake. looking at around 2,500 lbs boat and trailer

Looking at the costs I had decided on a replacement Vortec Crate motor running it with the TBI, short tube headers, better intake and MAYBE a cam swap? Looking for more low end to mid-range power.

I have been reading on LS swaps and have been seriously considering one. I understand the extra work that installing an LS would take, the extra work is not lost on me. I know an LS is a 'better' more advanced engine. But when it comes down to the practical, drivablity of a 300-325 hp engine am I really gaining enough to make it worth the extra work and expense? I had pretty much decided to go that way but having serious second thoughts. Just looking for some input.

[Fast355]

If you do a LS swap get a 6.0 or 6.2. The 4.8s and 5.3s are gutless unless you really spin them high. Even then a small cammed LQ9 6.0L with bolt-ons did not even make the same torque my mildly cammed 350 Vortec did at 3,400 rpm until 4,500 rpm. Same dyno, same day and the 6.0L truck had a 4L65E and 8.6 rear end vs my 4L85E and 9.5". The 6.0L also had electric fans where my 5.7 has a massive power sucking duramax clutch fan and HD fan clutch. 6.0L peaked at about 5,400 rpm in HP where my 5.7 peaked at 4,700. 272 rwhp @ 4,700 and 330 rwtq @ 3,200 from my 350 with the tiny 395' marine cam aka Ramjet/HT383 cam. I put the GM 357 HP 350 HO crate engine cam in it and bumped the power to 285 rwhp @ 5,500 /340 rwtq @ 3,800. Compared to the 395' cam power was better everywhere from 2,500+ My 5.7 has slightly worked heads with 2.02/1.60 valves, slightly higher compression from milled heads and a .016" thick shim head gasket, 1.7 rockers, tri-y headers, ported marine intake, and a decent exhaust. I recently dyno'd 12 rwhp and 3 rwtq more with open 2.5" cutouts between the cats and muffler for a total of 297 rwhp and 343 rwtq. That was also on E85 with 34* total timing. Even with the 215/223 @ .050 cam and the 1.7 rockers giving a .537" lift in my 350 the 6.0L with a smaller 212/218 high lift cam could not match the 350s torque until 4,500 rpm. Because of the head and intake design it went on to make about 20 hp more but gave up over 40 ft/lbs down in the 2,500 rpm range. With his driveline my numbers themself would have been about 5% higher. I already have a 4-bolt main 6" rod 383 sitting on the stand with a 10.5:1 compression ratio and Edelbrock Etec 170 heads. Cam will be a 224/236 @ .050 roller cut on a 108* LSA with .554/.554 lift. I am dropping the 1.7s and going with 1.5s this time around.

[Kudzu]

Since it is a street car I am more interested in low end torque. I have to keep reminding myself of this because it is easy to get caught up in HP search. If I go with an LS I am going to have to buy a used engine along with the harness to stay in my budget. If I could find a low milage total I could part it out and make some of the money back but not sure I really want to get into that much work. I have enough projects as is.

I am still thinking on this but the more I look at it I am leaning toward just buying a replacement Vortec engine and putting the TBI back in.

[lionelhutz]

Overall, I'm not sure it's worth it for what you would gain. You'd like driving a 6.0L LS more but the gains just might not justify the extra work in your case. Here is some info to consider.

A 5.3 LS will pull harder than the stock TBI engine and it will use less gas. The 5.3 LS would not have as much low end torque as the Vortec engine though so overall you'd have to spin it at a little higher rpm to get the same power. But, they love the rpm and it's not a big deal. You would hardly know you are doing it. Still, I'd consider it to be about even on drivability compared to the Vortec so the extra work to swap one really wouldn't be worth it unless you could do it cheaper.

A 6.0L LS beats a stock Vortec torque curve pretty much everywhere. Still, it's fairly evenly matched up to the Vortec peak torque. Then, the 6.0L pulls even harder up to it's own peak torque. However, add in the fact that LS engines love to rev so it's easy to turn them a little higher and the 6.0L will easily out-run the Vortec during normal driving. Don't believe anything about a stock Vortec having way more low end torque compared to a stock 6.0L LS because it's not true. Here are some numbers.

Vortec:
255 hp (190 kW) @ 4600 RPM
330 lb·ft (450 N·m) @ 2800 RPM
about 300 lb-ft @ 1400 RPM

first gen 6.0L
300 hp (224 kW) @ 4400 RPM
360 lb·ft (488 N·m) @ 4000 RPM
about 340 lb-ft @ 2800 rpm
about 300 lb-ft @ 1400 rpm

As another consideration, an electronic transmission is really nice if you spend the time to tune it. Fine adjusting the shift points to match your driving expectations can make a big difference in how nice you find the vehicle drives. You can pretty much get it to be in the gear you want all the time. You could also get this with the TBI by using a PCM and newer transmission.

[Fast355]

Overall, I'm not sure it's worth it for what you would gain. You'd like driving a 6.0L LS more but the gains just might not justify the extra work in your case. Here is some info to consider.

A 5.3 LS will pull harder than the stock TBI engine and it will use less gas. The 5.3 LS would not have as much low end torque as the Vortec engine though so overall you'd have to spin it at a little higher rpm to get the same power. But, they love the rpm and it's not a big deal. You would hardly know you are doing it. Still, I'd consider it to be about even on drivability compared to the Vortec so the extra work to swap one really wouldn't be worth it unless you could do it cheaper.

A 6.0L LS beats a stock Vortec torque curve pretty much everywhere. Still, it's fairly evenly matched up to the Vortec peak torque. Then, the 6.0L pulls even harder up to it's own peak torque. However, add in the fact that LS engines love to rev so it's easy to turn them a little higher and the 6.0L will easily out-run the Vortec during normal driving. Don't believe anything about a stock Vortec having way more low end torque compared to a stock 6.0L LS because it's not true. Here are some numbers.

Vortec:
255 hp (190 kW) @ 4600 RPM
330 lb·ft (450 N·m) @ 2800 RPM
about 300 lb-ft @ 1400 RPM

first gen 6.0L
300 hp (224 kW) @ 4400 RPM
360 lb·ft (488 N·m) @ 4000 RPM
about 340 lb-ft @ 2800 rpm
about 300 lb-ft @ 1400 rpm

As another consideration, an electronic transmission is really nice if you spend the time to tune it. Fine adjusting the shift points to match your driving expectations can make a big difference in how nice you find the vehicle drives. You can pretty much get it to be in the gear you want all the time. You could also get this with the TBI by using a PCM and newer transmission.

Actually the Vortec 350 makes as much as 40 ft/lbs more than a 6.0 down in the 1,200-2,000 rpm range, stock for stock. In the 2,200-2,500 rpm range it will brake stall the same converter more than 200 rpm higher. The 350 in my Express in stock form was making close to 280 hp @ 4,500 and 380 tq at the flywheel at 3,000 rpm if you go off the 25% expected drivetrain loss of a 4L80E and 9.5" 14-bolt. Stock intake & exhaust manifolds, factory 3" piping to the cats, factory muffler, factory 2002 5.7 Express 0411 tune, descreened maf, K&N filter and tb lip removed, MFI spider cranked to 66 psi to match the OEM spider. Oh I forgot I also had the EGR disabled in the tune and blocked off at the valve with a plate between the intake and valve.

[ras"86]

Great information, my stock 94 350 is due to be replaced soon, possibly a 350 vortec will be an easy fix.

[Queencityspeed]

The LS swap would be a lot of work with little gains over a decent SBC. Wiring, Mounts, Exhaust & etc. Bolt in a decent small block, tune it and ride out. Just my opinion.

[lionelhutz]

Actually the Vortec 350 makes as much as 40 ft/lbs more than a 6.0 down in the 1,200-2,000 rpm range, stock for stock. In the 2,200-2,500 rpm range it will brake stall the same converter more than 200 rpm higher. The 350 in my Express in stock form was making close to 280 hp @ 4,500 and 380 tq at the flywheel at 3,000 rpm if you go off the 25% expected drivetrain loss of a 4L80E and 9.5" 14-bolt. Stock intake & exhaust manifolds, factory 3" piping to the cats, factory muffler, factory 2002 5.7 Express 0411 tune, descreened maf, K&N filter and tb lip removed, MFI spider cranked to 66 psi to match the OEM spider. Oh I forgot I also had the EGR disabled in the tune and blocked off at the valve with a plate between the intake and valve.

I don't care at all about your numbers. You have posted enough complete bullshit to show that none of them have any credibility. Previous crap like claiming numbers that the performance magazines with their typical over-inflated tests NEVER come close to matching with or that an engine with a cold-air intake and catback can put 50 ft-lbs more wheel torque down then it's factory rated flywheel torque. Add in the fact that you hate LS engines and you have no credibility. I liked the old small blocks and still have a few around, but have no trouble admitting that the LS engines can make more power.

You are completely full of shit about the L31 making up to 40 ft-lbs vs the 6.0L. Anyone who can use Google can look up this curve.



The LQ4 certainly DOES make hit 300 ft-lbs of torque in about the 1300-1400 rpm range. Add 40 ft-lbs and you're over the L31 peak rated torque.

Any claims about how a L31 does way more than rated after you do the simplest bolt-on mods is bullshit. Tons of people have proved that mods like MAF de-screening, TBI lip removal or catback exhausts pick up very minimal power.

Any claims about how a L31 picks up a bunch of power after more serious bolt-ons or a cam and tuning would also apply to a LQ4. It's not hard to find power in a LS engine with smart modifications and tuning.

[Fast355]

I don't care at all about your numbers. You have posted enough complete bullshit to show that none of them have any credibility. Previous crap like claiming numbers that the performance magazines with their typical over-inflated tests NEVER come close to matching with or that an engine with a cold-air intake and catback can put 50 ft-lbs more wheel torque down then it's factory rated flywheel torque. Add in the fact that you hate LS engines and you have no credibility. I liked the old small blocks and still have a few around, but have no trouble admitting that the LS engines can make more power.

You are completely full of shit about the L31 making up to 40 ft-lbs vs the 6.0L. Anyone who can use Google can look up this curve.



The LQ4 certainly DOES make hit 300 ft-lbs of torque in about the 1300-1400 rpm range. Add 40 ft-lbs and you're over the L31 peak rated torque.

Any claims about how a L31 does way more than rated after you do the simplest bolt-on mods is bullshit. Tons of people have proved that mods like MAF de-screening, TBI lip removal or catback exhausts pick up very minimal power.

Any claims about how a L31 picks up a bunch of power after more serious bolt-ons or a cam and tuning would also apply to a LQ4. It's not hard to find power in a LS engine with smart modifications and tuning.

I guess anyone can google this power chart too and realize what a L31 with a decent intake manifold will do. Remember he said nothing of using the stock Vortec truck intake manifold. The factory Marine cam is really no hotter than the truck cam. Marine L31 is 292 HP @ 4,800 and 370 TQ @ 3,200 with more than 350 ft/lbs @ 2,000 rpm. But what do I know. I have run a stock long block L31 in a TBI application with shorty headers and a 454 TBI unit on top of an edelbrock performer rpm intake manifold. It made over 300 HP at the crank and over 400 TQ at the crank. It did 260 RWHP/330 RWTQ through a 700r4 and 8.5 10-bolt with TBI.

http://www.gmpowertrain.com/2013_pdf...ine_010713.pdf

As for your factory rated power vs wheel power. My 2012 Titan put down 398 RWTQ on a stingy ass Mustang dyno and 296 RWHP after power correction. Real power was 6% higher than the correction in 45*F weather. The truck made over 300 RWHP and 400 RWTQ un-corrected. Same truck on a Dynojet made 330 RWHP. Factory rating was 317 HP and 385 TQ. Cold air intake, muffler swap, and a Hypertech programmer was all it had. On a 60*F sunny day on a decent track, it ran a 13.98 @ 98 on a 2.01s 60' with an open differential and well worn P275/60R20 Goodyears wrangler SRAs.

MAF descreen, TB lip removal, and K&N kept my MAP sensor from dropping above 3,500 rpm on the stock L31 setup. All stock it would pull down to about 90-92 KPA by 5,000 rpm on a 99-101 KPA baro. After the changes it would hold 96 KPA all the way to the 5,600 rpm fuel kill. The descreen also leaned the over-rich WOT air/fuel ratio down nearly a full point on stock tune. It was one of the first things I messed with and had a HUGE impact on how it ran.

[Fast355]

I have also seen numerous stock longblock, stock cam, stock intake manifold, stock head 350 vortecs put down more than 320 RWTQ once you open up the horrendous exhaust system they came with from the factory. The manifolds are not the worst part of MOST stock L31 engines. My Express van just happened to have a better factory exhaust system than any other factory LD L31 GM vehicle. Most of the trucks and SUVs used tiny 1 7/8" exhaust pipes between the manifolds and the mufflers with smaller cats. The Express van came out of the manifolds at about 2.5" and stepped up to 3" less than 6" off the manifolds and ran all the way to the muffler at dual 3". Makes a tremendous difference in power even with the stock manifolds.

[lionelhutz]

The numbers I posted are for the truck L31, not the marine engine. The marine cam had > 0.020" more lift and > 5* duration so they are not the same.

Claims that a manufacturer would leave 75+ ft-lbs of torque on the table by installing a terrible intake filter or muffler are grossly exaggerated.

[Fast355]

yeah it did....

this forum isnt about top performance or ideal engines, its about taking whatever you have and making it run the best you can.

in the end, a junkyard 305 with a carb would make you happy too.

Haha it did in my Vette. 305 that had been in my 1983 G20. Had atleast 300K on the block, 120K on the rebuild and had blowby oil blow out of the passenger valve cover at high rpm. Slapped some Vortec 059 305 heads on it with a little port work, a nice thumpy Crane 272H10 flat tappet cam, performer dual plane with a tweaked Q-Jet, a 150hp shot of nitrous, and some cheap long tube headers with a Pypes 2.5" dual exhaust. Had a junkyard powerglide with a 2,800 stall and 3.07 gears. It got me booted off the track for lack of safety gear for the time it ran on motor much less spray. I put an victor jr with a plenum divider plate I fabricated and edelbrock 500 cfm and picked up even more top-end power.

My whole point is the L31 swap is 10x easier and will fit what the OP wants best so why mess with the LS swap when he will gain literally nothing for his goal.