Whats your impression of a 5.3L LS motor in these trucks?

[LEEVON]

We went to see a guy this weekend, Dad was looking for a takeout 5.3L and this guy gets them ready, wires, tunes and runs them on a stand. I was telling him about my carbed 5.3L build. I also explained that the reason for the carb is the hot rod theme of the truck, looks and to be different. His exact words were "you ruined it" to which I replied "When was the last time you built a 400hp small block for $500?". Good point, he says. Cheap, clean power no matter how you get the fuel in there!

[69GWC]

Originally Posted by 68Stepbed

It's not that they make THAT much more power, it's the WAY they make it. The valve angle allows for a different flow path of air/fuel for better atomization at higher rpms when the air gets turbulent, which makes for more power and better efficiency. This along with the lighter weight rotating assemblies, will allow for power levels to climb well into 6500-7000rpm ranges. Any old small block is pretty much spent by 5500 unless you start throwing alot of go-fast goodies in it. Keep in mind these are the same "type" of go-fast goodies that LSx motors come with in stock form.

The one advantage old sbc/bbc engines have is low end grunt. The 23 deg valve angle allows for better fuel atomization at low rpms, but is limted at higher rpms, which is still much better for a towing application.

This is what I was talking about on the 5.3s vs the 350, If your pulling something all the time the 5.3 in stock forum does not do it as well as the 350 at all. I am pulling a 5x10 trailer every day and just dont like the fact that the power is all way up in the rpm band and to use it your screaming the motor all the time.
Now If your just wanting fast, hotrod or whatever Iam sure the 5.3 would be the ticket.

{Not directed at anyone just saying}
I still find it hard to believe people getting over 18/19mpg and of these motors, my 06 Z71 with a 5.3 and 3.42 gears has only one time ever even hit the 19mpg range and that was on flat level ground doing 55mph with the wind behind me, truck is pretty much idleing at those speeds.

As of right now pulling my 5x10 trailer every day Iam getting 12mpg and with out it I normally get 14/15mpg.

Iam far from a motor expert just what I have found after driving both motors in similar trucks and gearing for the last few years. I would have had a choice when I bought the 06 I for sure would have bought a 5.7 for how I use it over the 5.3.

[CC69Rat]

My GMC sees maybe 1800 RPM if that (right now) Maybe some cones later but .. Definitely not the drag strip. Most of the time it's putting down an old back country road with my arm on the door frame. 3:08 geared, 255hp 350 with a 3OTT and 55mph. I'm getting 20mpg, minimum.

[Jon01]

LS motors make incredible power due to their head design coupled with EFI and modern spark control.
You can make them to everything but sit up and beg with a laptop.
I've had a few LS powered cars(02 SS, 05 GTO, 06 TBSS) and the motors simply never fail to amaze in what they can do.
Ex: I bought my GTO new, by 800 miles it had an MS3 cam, Kooks headers, FAST intake and I'd done a full VE tune.
It put down 456rwhp, got 24-25mpg on the interstate running 75+ with the air cranked and rode like a cadillac. It'd also trap ~94-96mph in the 1/8 mile on 19" tires. Stone stock shortblock and cylinder heads other than valve springs.
Find me an old 350 that will do that with just those mods.

I bought my 5.3 with 80k complete intake to pan with accessories, harness and PCM for $500. $200 4L60E.
I can hack the harness and do the PCM myself with HPTuners.
It'll be getting either a GM hotcam or 228r cam, Circle D converter and a set of headers. I look for it to make around 350 at the tire which would put it well over 400 at the crank.
Were I not doing the cam and other mods I'd have it in and running for about a grand. I'll probably have about 2 in it with the mods though but a stock LS motor is like having a cold beer and not drinking it.

There's no reason it shouldn't get 20+ on the interstate with the converter locked, my wife's Tahoe gets 18-20 going 70-75 after I tuned it and messed with the MAF curve/VE table using HPTuners and my wideband.

Would I pull a good running 350 and replace it with a 5.3?
Yup, that's what I plan on doing this weekend and not doing it just to fit in, doing it for all the reasons stated above.
Anybody want to buy a good running, smoke free 71 350 with all accessories, ram horn manifolds and an Edelbrock intake?

[CC69Rat]

Originally Posted by Jon01

LS motors make incredible power due to their head design coupled with EFI and modern spark control.
You can make them to everything but sit up and beg with a laptop.
I've had a few LS powered cars(02 SS, 05 GTO, 06 TBSS) and the motors simply never fail to amaze in what they can do.
Ex: I bought my GTO new, by 800 miles it had an MS3 cam, Kooks headers, FAST intake and I'd done a full VE tune.
It put down 456rwhp, got 24-25mpg on the interstate running 75+ with the air cranked and rode like a cadillac. It'd also trap ~94-96mph in the 1/8 mile on 19" tires. Stone stock shortblock and cylinder heads other than valve springs.
Find me an old 350 that will do that with just those mods.

I bought my 5.3 with 80k complete intake to pan with accessories, harness and PCM for $500. $200 4L60E.
I can hack the harness and do the PCM myself with HPTuners.
It'll be getting either a GM hotcam or 228r cam, Circle D converter and a set of headers. I look for it to make around 350 at the tire which would put it well over 400 at the crank.
Were I not doing the cam and other mods I'd have it in and running for about a grand. I'll probably have about 2 in it with the mods though but a stock LS motor is like having a cold beer and not drinking it.

There's no reason it shouldn't get 20+ on the interstate with the converter locked, my wife's Tahoe gets 18-20 going 70-75 after I tuned it and messed with the MAF curve/VE table using HPTuners and my wideband.

Would I pull a good running 350 and replace it with a 5.3?
Yup, that's what I plan on doing this weekend and not doing it just to fit in, doing it for all the reasons stated above.
Anybody want to buy a good running, smoke free 71 350 with all accessories, ram horn manifolds and an Edelbrock intake?

[Jon01]

Mature.

[Hubscrub]

The only newer motor i've seen i like is 68 stepbed's. I'm not a fan of the new stuff i don't care if it make more power or mileage. Everybody is different i like Inline 6's over a V8 i like 305 is that a reason to dog on these motors no. Drive what you want i do, i drive a fuel injection almost daily but i don't want it in my weekend rides if you tune it right they run just as good and look sweet. and my laptop stays on my desk

[CC69Rat]

Originally Posted by Jon01

Mature.

Relax Bro. All I meant was read the rules on posting For Sale items. You have to be a member to post for sale.

I asked for knowledge on the LS motors, and understanding 'why' That's all .. But Matt's post said it best. Why are these magic LS motors making so much power? That's all I'm looking for. If I had the $4k was it (?) to lay down for an LS, .. absolutely. I'd be all in. But, to just sh1t can my 3970010 matching numbers 350 and drop in the LS so I can drive the same speed and get the same fuel mileage. For ME, and MY usage, it just doesn't make sense with what I know about them. WHEN I start running cones and playing with my GMC, maybe.. but I'm not going to starve to make it happen. I am adopting (more than likely) from Brazil in the next few months, so I'm sticking with what makes sense right now. Just learning..

[Jon01]

LS motors make killer power because they have EXCELLENT cylinder heads and full spark control creating a very efficient engine.

Here's a good read:
http://houstonperformancetrucks.com/...h-flow-numbers

Look at the runner volumes on them as well as the flow rates.
They have huge intake runners and flow incredibly well. Stock, unported 799 and 243 heads flow nearly as much as Dart Iron Eagle 200 Gen 1 heads on the intake side and outflow them on the exhaust.
This coupled with modern cam designs really let them breathe.

You can do the swap for well under 2k if you can chop the harness up yourself and have a local shop to shut the VATS off in the PCM.
There's a place up here that sells complete takeouts with full harness and PCM for $500, I can give you their # if you'd like. Nice guys and always have a couple kicking around.

I'm yanking the 350 but in the end it probably won't be sold, I'm a firm believer in keeping original stuff with the vehicle should someone ever want to return it to OEM. All my stuff that's modded has the original block shoved in the corner just in case. Mostly said that to be sarcastic. I'd probably have a hard time letting it go w/o feeling bad about separating it from the truck.

[19seventeeCustom]

I pulled a perfect running 350/700r combo out in favor of an ls1,
couldn't be happier I did. I wanted leak free, reliable, and more hp than what
my sbc was giving me.....and guess what?...I succeeded.

Throwing money at a 35yr old motor just wasn't appealing to me......but then again,
i'm not old school. pound for pound you CAN NOT beat lsx power and tune ability.

Bottom line though, new tech is here to stay and the bar is only being raised with gen5
bring it on.........

[Danny Bost]

I love my 71 350/350 combo. That being said though, I drive a 2007 3500 6.0 with a fully loaded utility bed on a daily basis. I weigh in just shy of 10K without pulling anything and I still average about 11 MPG. When I drop the hammer on it on the highway I am not at all disappointed. Yes, it does run in the higher RPM range, but that does not bother me. I would put one of these in my truck in a heart beat if I could afford it. I love the dependability and overall performance. Just my opinion.

[69GWC]

Yep I had a 02 2500HD 4x4 ex cab with a 6.0l and 4.10 gears, got 11/12mpg like clock work ran good on the hwy but IMO lacked low end pulling power and I mean for getting the load going from a stop as once it was going it did fine. I think if the tranny was geared lower the truck would have pulled better but first and second gear are geared so high its hard to get the power to the ground when pulling anything.

Most people dont believe me but I did show a few friends of mine how that truck would run 95mph before it would shift out of 2nd gear and I think it was like 50mph before it would shift into 2nd gear out of first, I mean how is something like that going to pull anything very well.
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[CC69Rat]

LS for me as soon as I can, but not anytime soon. Makes sense, all things considered. Thanks.

[Wasted Income]

I'm fully converted to LS. The amount of f*cks I give about Gen I or II SBC stuff is less than zero.

My only regret is not doing it years ago.


Wait.....I mean....they suck...you guys who haven't converted want nothing to do with them. They are junk.


(Maybe that will keep the junkyard prices from rising AS fast as they have been....)

[68Stepbed]

[Heavymetl]

Originally Posted by Wasted Income

I'm fully converted to LS. The amount of f*cks I give about Gen I or II SBC stuff is less than zero.

My only regret is not doing it years ago.

Same here. Its one thing to read on internet boards about the LS, but once you spend some time behind the wheel of a LS powered hot rod (not a stock 5.3 truck), you'll NEVER go back to old school. The ease at which these engines make big power is astounding. Its like magic...but its real.

[el_diablo]

Originally Posted by 69GWC

Yep I had a 02 2500HD 4x4 ex cab with a 6.0l and 4.10 gears, got 11/12mpg like clock work ran good on the hwy but IMO lacked low end pulling power and I mean for getting the load going from a stop as once it was going it did fine. I think if the tranny was geared lower the truck would have pulled better but first and second gear are geared so high its hard to get the power to the ground when pulling anything.

Most people dont believe me but I did show a few friends of mine how that truck would run 95mph before it would shift out of 2nd gear and I think it was like 50mph before it would shift into 2nd gear out of first, I mean how is something like that going to pull anything very well.
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What tires did you have on that thing that it would shift at 50 & 95mph with 4.10s and an auto transmission?

[BIGBLU 72]

What I plan on doing is a 5.3/t56 and I KNOW a old style SBC won't touch my gas mileage. I know I'm not going to have the grunt of my 406 but when a 5500+lb stock Silverado SS smokes my 68 w a 406 everytime it's hard to Make an argument. The 406 gets 8mpg the SS gets 17 highway and it's AWD. Def not pullin the 406 to swap a 5.3 but a second 67/72 is in the future. My uncle put it best "I love my 350 in my 72 (Vette) but its a lot more fun roasting the tires then gettin 30 mpg in my 04 (Vette)"
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[BrutonLS1]

Still running hoses and finishing up wiring, but here she is.

[69GWC]

Originally Posted by el_diablo

What tires did you have on that thing that it would shift at 50 & 95mph with 4.10s and an auto transmission?

At that time it had 305s (33s) on it, but the shift points where not that much different on the stock tires just did not remember the numbers for sure.
If that thing had a low geared tranny I bet it would have been a hoss.
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[Vintage Windmills]

Keep in mind the LS series is not without problems. I've experienced it firsthand in 2 of my trucks as follows:

Stay away from the 99's unless your running an aftermarket intake. These early manifolds could warp and loose their seal. I had it happen on my 99 truck and its been documented online. Dorman later revised the design so it did not warp.

Also my 6.0 lq4 leaks some oil with only 88,000 miles. Thinking Its a good reason though to pull it and do cam/tune/headers and get 450 ft lbs. I do like this engine overall.

I'd like to hear more comments on 96-98 vortec 350's vs. LS 5.3 liters. I've had both in stock form and I'd say (in stock form) the LS1 has little if anything over the vortech. Making mor horsepower per dollar I see the LS1 taking the lead though.

[68Stepbed]

Originally Posted by Vintage Windmills

I'd like to hear more comments on 96-98 vortec 350's vs. LS 5.3 liters. I've had both in stock form and I'd say (in stock form) the LS1 has little if anything over the vortech. Making mor horsepower per dollar I see the LS1 taking the lead though.

Do some reading on LS1truck.com Lots of swaps and other info there about that.

[BHyatt]

I attended a swap meet this Sunday in Indianapolis and could not help but notice the extreme increase in Intake Manifolds and Carb's for sale. I think that the tide is turning away as technology becomes easier for everyone to adapt.

[Ackattack]

Originally Posted by Vintage Windmills

I'd like to hear more comments on 96-98 vortec 350's vs. LS 5.3 liters. I've had both in stock form and I'd say (in stock form) the LS1 has little if anything over the vortech. Making mor horsepower per dollar I see the LS1 taking the lead though.

I've only had one vortec 350 (~110k when I sold it), but I had more issues with it than all of the LS engines I've had (8 or so of them including my suburban with 157k and still kickin strong).

Stock power wise and fuel efficiency not much difference for everyday driving/towing.

[Hubscrub]

I've got a 305 vortec with 200,000 + been a very good engine not problems ever it's a 97 (I know not a 5.7) it will pull haul without issue
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