5.7 vortec or 5.3LS?

[98chevy2500SS]

After buying an 05 GMC Sierra 2500HD with the 6.0L Vortec, I'm in love with the LS engines. If I had to chose between a 350 and a 6.0 LS, hands down LS any day.

 

[Supercharged111]

After buying an 05 GMC Sierra 2500HD with the 6.0L Vortec, I'm in love with the LS engines. If I had to chose between a 350 and a 6.0 LS, hands down LS any day.

I'll line my 1500 up with that 6.0.

 

[L31MaxExpress]

After buying an 05 GMC Sierra 2500HD with the 6.0L Vortec, I'm in love with the LS engines. If I had to chose between a 350 and a 6.0 LS, hands down LS any day.

Having owned, driven, tuned and towed with both. 5.7L all day, everyday. I HATE the LS when it is naturally aspirated. Zero torque, all revs and no go. A stock L31 with headers (stock logs on the SBC are trash) will leave a 6.0L far behind it on a hill, both dragging 6-8+K lbs. The stock 5.7 using an equal gear in the same size vehicle will get the jump on a 6.0L off the line and stay ahead of it past the legal speed limits in most states. The 6.0L is a little smoother running and makes power at a higher rpm but it is absolutely gutless under 3,500 rpm and uses more gas. When it comes time to rebuild the 350, shove a 383 rotating assembly in it and a decent torque cam and it runs circles around a cammed 6.0L especially towing. With the old 350 even, I never had a 6.0L truck towing a similar load pass me uphill as I was the one passing the 6.0L.

 

[L31MaxExpress]

I'll line my 1500 up with that 6.0.

I will line my Express up against it and would have with the 350 even when it only had shorty headers on it too. Only way he would win is if I blew the tires off.

My buddy has an 06 1500HD crew cab with factory 3.73s in it. He put a small BTR towing cam in a 10,000 mile LQ4 and put in the truck. It is tuned as well. Its is an absolute PIG as far as power goes. 13 mpg highway on a good day. I don't think it could spin the stock size tires in the rain.

 

[RDF1]

Oh na they are stock. And warped now. But gooseneck had electric over hydraulic brakes.

Yikes! Hopefully you've upgraded the brakes...probably wouldn't matter with that much weight behind you anyways.

 

[L31MaxExpress]

Oh na they are stock. And warped now. But gooseneck had electric over hydraulic brakes.

I would be afraid to admit to towing that much. It has been a while since I have looked but around here it is something like 24,000 GVW requires a CDL and DOT would have you impounded with that kind of load.

 

[RDF1]

It's all in how you drive it also. I can get 16 in my 2500hd with 4.10s and 33s. It gets 12-13 with empty car hauler and 10.5-11 loaded. It even got 8mpg hauling that 38,5000# load of lumber.

I've got a 43 gallon tank/toolbox in the bed and the 26 gallon stock tank. Ive gone over 700 miles loaded and over 1000 miles without a trailer.
My poor old turbo 6.0 half ton has gone a little over 600 miles on a 26 gallon tank almost every time I've taken it out of state.
Lots of timing, really lean AFR and the right plugs with 93 octane was all it took.

I spent a few hours tuning a buddys 1999 K1500 vortec 355ci with a stock cam with 35s and 4.56s and I tried all of my LS tuning tricks to try and help it out. It was enough to get him 3.5MPG better than it got with the old 5.7. We used a whole box of spark plugs tryin to get a read on them after hauling a trailer to get TCC unlock and downshifts decent and playing with timing and PE AFR.

I dont know what kinda secret sauce your trucks have but he hasn't been to thrilled with his older trucks and I can't tell the old vortec pulls my car hauler with a 4500# truck on it better than my 6.0. I get better mileage than him and I can hold my speed no problem.

That turbo 6.0 I had in my half ton tho.. with 7500# behind it at 2000 rpms, it chugs on like a diesel.

I will line my Express up against it and would have with the 350 even when it only had shorty headers on it too. Only way he would win is if I blew the tires off.

My buddy has an 06 1500HD crew cab with factory 3.73s in it. He put a small BTR towing cam in a 10,000 mile LQ4 and put in the truck. It is tuned as well. Its is an absolute PIG as far as power goes. 13 mpg highway on a good day. I don't think it could spin the stock size tires in the rain.

 

[RDF1]

I would be afraid to admit to towing that much. It has been a while since I have looked but around here it is something like 24,000 GVW requires a CDL and DOT would have you impounded with that kind of load.

It's over and done now. Deputy pulled me over for going too slow in the fast lane. 65 in a 70
He mentioned the load but just told me to get over in the right lane. Won't be doing it again with that truck. But it was quite a ride. The air ride gooseneck and air bags on the truck really made for a smooth trip.

 

[L31MaxExpress]

It's all in how you drive it also. I can get 16 in my 2500hd with 4.10s and 33s. It gets 12-13 with empty car hauler and 10.5-11 loaded. It even got 8mpg hauling that 38,5000# load of lumber.

I've got a 43 gallon tank/toolbox in the bed and the 26 gallon stock tank. Ive gone over 700 miles loaded and over 1000 miles without a trailer.
My poor old turbo 6.0 half ton has gone a little over 600 miles on a 26 gallon tank almost every time I've taken it out of state.
Lots of timing, really lean AFR and the right plugs with 93 octane was all it took.

I spent a few hours tuning a buddys 1999 K1500 vortec 355ci with a stock cam with 35s and 4.56s and I tried all of my LS tuning tricks to try and help it out. It was enough to get him 3.5MPG better than it got with the old 5.7. We used a whole box of spark plugs tryin to get a read on them after hauling a trailer to get TCC unlock and downshifts decent and playing with timing and PE AFR.

I dont know what kinda secret sauce your trucks have but he hasn't been to thrilled with his older trucks and I can't tell the old vortec pulls my car hauler with a 4500# truck on it better than my 6.0. I get better mileage than him and I can hold my speed no problem.

That turbo 6.0 I had in my half ton tho.. with 7500# behind it at 2000 rpms, it chugs on like a diesel.

Biggest problem with the truck/suv 1500 5.7 Vortec is the tiny pipes used for the exhaust closely followed by the stock exhaust manifolds. In factory form it is horribly choked up. Its not the engines fault though and inexpensive power and MPG to be gained. My first change on my 350 was tuning, closely followed by shorty headers, a drop in K&N filter and throttle body lip removal.

Another thing that adds a noticeable amount of torque is re-adjusting the valve train. FSM shows for 1-full turn from Zero lash. Every hydraulic lifter small block I have messed with likes 1/4 turn of preload on the lifters. I do a running adjustment to find zero lash, then 1/4 turn past the zero lash point where they stop tapping. Since we do not drive a dyno at peak HP the looser preload mimics the shorter pushrod test Holdener did and the 350 gains a good chunk of torque as well as helps the weak stock valve springs stability at high rpm. I have witnessed a GM sealed 604 crate engine gain 30 ft/lbs of torque and 500 useable rpm up top merely backing off from the factory 1 turn lash to 1/4 turn. For a super cheap upgrade, 8 stamped 1.6 self aligning rockers on the intake valves alone also really perk up a stock cammed L31 by adding 0.030" of lift and about 2-3° duration throughout the curve. You can put 1.6s on the exhaust but that will lose some torque under 3,500 rpm by blowing down the cylinder more quickly. Above 3,500 rpm that helps but for lower rpm torque and fuel economy it does not. My 383 currently has 1.7 intake and 1.5 exhaust rocker ratios. At 2,000 rpm it is up 15 ft/lbs from the straight 1.7 rocker setup and only gave up 3 hp at 6,000.

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As far as tuning for, its much like you say. Lean it out and crank up the timing. Mine liked 16.5:1 air fuel ratio and as much as 45° of timing. Cruising lean the 350 does not like rebreathing its own exhaust gasses. Exhaust contamination of the intake charge actually hurt fuel mileage on my Vortec 5.7L if you catch my drift. Eliminating that contamination fixed a tip-in hesitation it had under 10 mph from day one and added a noticeable amount of off-idle torque. The 02 sensor target voltage also needs to be altered. I have run as low as 250mv in the first 3 cells and slowly ramp back up to 550mv in the highest cell. With a P01/P59 I actually use lean cruise on them.

 

[Trio]

You lost me at road salt - I would start with a different truck.