Carb SBC vs TBI SBC vs Gen 3 LS reliability

[slow_c1500]

Hey guys. As some of you may already know, I’ve had (and am still having) horrible luck with my 5.7 vortec. While i still plan on fixing it, I am tired of the spider injection and all the crappy plastic parts, and I never want to own one of these vortec SBC’s again. I am looking at other potential engine options to either swap into my current truck or buy a different truck with such an engine in it.

So between the carbed SBC, TBI SBC, and Gen 3 LS, what is the most reliable? What are the common issues with each one? We don’t have to go into the power and mpg part of it, I am just curious about sheer reliability. Thanks! And we all know TBI sounds the best

 

[BeXtreme]

You are never going to beat a modern LS for reliability, or power, or fuel economy. There is really no major wear components on them. Change the oil every 5,000 miles or so. Change spark plugs and wires ~100,000 miles... that's it. I've got 230,000 miles on a Gen IV 5.3 that we use to haul the family all over the PNW and tow our ~6k lb travel trailer and the engine has never had an issue. Basic maintenance items and that's it. I've had to rebuilt the trans and just had the radiator start leaking last month coming back from a trip. Other than that, nothing.

 

[Schurkey]

The LS and "new" LT have valvetrain problems when they're new enough to have the cylinder-deactivation "feature". That can be fixed. Piston slap is sometimes an issue. Other than that...great reliability/durability because of tight computer control and decent casting machining processes--except for Castech-sourced cylinder heads.

The injected small-blocks have great reliability/durability aside from distributor problems with Vortec and LT "optispark"; and some piston-slap issues. Decent casting/machining processes in most cases. Most of the previous oil leak issues solved. Again, computer control contributes to durability and reliability.

Carb'd small blocks have reasonable reliability IF the distributor and carb are maintained, and the oil leaks are controlled. "Adequate" but not exceptional durability, and only if the oil is changed frequently and the PCV works properly. Crappy--or no--computer control of fuel mixture leads to cylinder-wall wear, oil contamination, and then ring problems. Not much for piston-slap due to enormous skirts on the heavy pistons. Some had "lightweight" heads known for cracking. All had flat-tappet cams that are now a problem due to quality issues with cams/lifters...but even GM had secret warranties on flat cams in the late '70s--early/mid '80s. If you don't like the reliability/durability of a Vortec, you sure as hell are not gonna be happy with a old carb'd engine--and probably not with a "new" carb'd engine.

 

[slow_c1500]

Thank you guys for the responses! At this point I can probably rule out carbs. So between the TBI small blocks and LS engines without AFM, I am getting the sense that the LS is just the best option. I have also heard that the LS engines seem to have less leaks and less electronics/sensor failures. Is this true as well?

 

[BeXtreme]

Thank you guys for the responses! At this point I can probably rule out carbs. So between the TBI small blocks and LS engines without AFM, I am getting the sense that the LS is just the best option. I have also heard that the LS engines seem to have less leaks and less electronics/sensor failures. Is this true as well?

The only leak you are likely to have on an LS is if you replaced a component(front cover, rear cover, oil pan) and didn't align the parts correctly. All of the gasket surfaces are machined and the gaskets are rubber o-ring impregnated in aluminum sheet, so you can't really destroy the gaskets by overtorquing them anymore and they last forever. My 230k mile 5.3LS has no leaks whatsoever and it is also an AFM/VVT motor. I just got a 6.2L Gen IV to replace it out of a 2009 Denali that a guy was parting out. It has ~160k miles on it and looked brand new inside when I tore it down. This one is a VVT motor, but no AFM. The AFM lifters have been known to collapse. The Gen III LS motors have been known to have rocker trunnion failure issues if you are running huge lift. The Gen IV valvetrain is pretty bulletproof. An AFM/VVT engine can have all of that deleted very easily and most of the time you can get a cam kit with a AFM delete all at the same time for ~$1K

 

[BeXtreme]

Just about all the electronics on the LS engines is solid state and has very little wear/issues. I've never had an issue on any electronic parts on any of mine. I am sending the injectors out from the 6.2 for a cleaning and flow balance check, but it ran fine when it was pulled.

 

[slow_c1500]

So essentially what I have gathered for the problems on the two generations:

Gen 3 has piston slap and rocker trunnion issues with high lift (I probably wouldn’t need to worry about this, I’d keep the motor stock)

Gen 4 has AFM and VVT

 

[PlayingWithTBI]

Meh, I vote TBI but, that's just me

 

[Schurkey]

I vote for fixing the existing Vortec. But this isn't a poll, and my vote doesn't actually count.

 

[618 Syndicate]

LS motors are dead reliable and take abuse well. I personally have a 6.0 with over 300k on it, and a 5.3 with over 275k. Both leak a little, and valve guides are worn causing a bit of smoke on starting, but I'd drive either one of them cross country tomorrow.