5.7 vs 5.3

[Hezsus]

Our 5.3's get better mileage towing than I do, but if i leave it in 3rd Its pretty easy towing.
we have a 2002 5.7l express van that regularly hauls our 9000lb trailer, and it does better than my 5.7 or any of our 5.3's or 4.8's.

 

[DieselPower]

Gearing is everything. A LS motor is designed to provide more power and in stock form has some pretty nice upgrades over a stock 350. Better spark, better flowing heads, better induction system, - it's just a higher performance engine right out of the factory. It is built to handle higher RPM's, giving more high end power and losing some torque on the low end as a result. Going stock on both motors, the LS will want some lower gearing in order to better utilize its power advantage - but given that it should easily outperform a stock SBC. Realistically a TBI engine doesn't perform much better than a mid-70's, detuned, emission-laden SBC. The potential is there though - with a decent cam, stroke it, head upgrades, improved induction and a decent exhaust - you can make a pretty good towing machine out of it. Target low end torque and put in some decent gearing and the LS motors would be hard-pressed to match the towing capability. The SBC makes pretty good low end torque - which really helps in towing anything heavy.

 

[ccreddell]

TBI motors have enormous potential. The guy over at TBIchips.com is getting 300+HP and 20+MPG out of them pretty easily.

 

[DieselPower]

TBI motors have enormous potential. The guy over at TBIchips.com is getting 300+HP and 20+MPG out of them pretty easily.

Not from a stock tune with all stock parts. Yes, all SBC's have enormous potential. I've pulled 400+ hp and gotten 22 mpg out of one without Nitrous or forced induction - and that's nothing special. "TBI" motors are just low compression SBCs with a mild cam, marginal heads and a cheap fuel injection system - like a detuned 70's vehicle (only they came with a carb on it). Start upgrading those parts and the potential becomes realized.

 

[ccreddell]

Nobody was talking about a stock-unless i missed something. Hes putting vortec and roller cam-basically a vortec shortblock-with a TBI and a tune.

 

[DieselPower]

Nobody was talking about a stock-unless i missed something. Hes putting vortec and roller cam-basically a vortec shortblock-with a TBI and a tune.

There is some mixing and matching of various SBC models and the overall topic is a comparison of a 5.7 vs a 5.3 LS in towing. A vortec head seems to make the entire motor a vortec motor, but a TBI induction system made the engine a TBI motor (generically, no particular individual references here.)... I was trying to be more specific with what constituted a "TBI" motor so that nobody was missing anything. If you swap out the heads and cam, it's no longer the "wimpy" stock TBI engine. No disagreement on the potential of the SBC on my part - but the components used in the engine dictate what the potential is. The OP's question implies stock motors and some responses do not make that same assumption. Regardless of which motor is in place, I'm just pointing out that gearing is going to matter at least as much as the engine.