Carb SBC vs TBI SBC vs Gen 3 LS reliability

[Leeztruk]

I just put a 4.8L in my '89 Cheyenne and I love it. Not hard to do if you plan accordingly. Now to throw a little rain on your parade. I see you're from sunny California with emissions regulations that could strangle most swaps (I'm guessing here, as I live on the Right coast). I've read that a swap can be made but the engine/trans swap MUST meet the same requirements as the year of that engine donor, and be able to pass CARB inspection. I would strongly suggest you talk to your DMV about rules and regulations BEFORE you get into an LS swap. In my state (CT) emissions testing/inspection is not performed on vehicles older than 25 yrs., so a swap to LS is not only doable, but a cost effective way to save an older truck such as ours

 

[slow_c1500]

I just put a 4.8L in my '89 Cheyenne and I love it. Not hard to do if you plan accordingly. Now to throw a little rain on your parade. I see you're from sunny California with emissions regulations that could strangle most swaps (I'm guessing here, as I live on the Right coast). I've read that a swap can be made but the engine/trans swap MUST meet the same requirements as the year of that engine donor, and be able to pass CARB inspection. I would strongly suggest you talk to your DMV about rules and regulations BEFORE you get into an LS swap. In my state (CT) emissions testing/inspection is not performed on vehicles older than 25 yrs., so a swap to LS is not only doable, but a cost effective way to save an older truck such as ours

The LS swap wouldn’t take place in the immediate future, i am just planning ahead. I was already planning to move to a different state with less strict laws.

But say if my swap did have to meet the California requirements, as long as I don’t mess with any emission devices, it should be fine right?

 

[Schurkey]

if my swap did have to meet the California requirements, as long as I don’t mess with any emission devices, it should be fine right?

As long as all the emissions devices that were applicable to the LS donor vehicle are retained...
The donor vehicle probably has to match or be similar GVWR to the receiving vehicle.
LS computer to match the LS engine.
LS wire harness to match the LS computer.
Additional O2 sensors and maybe a second catalyst.
Donor vehicle fuel tank and vapor control system
God knows what else. Might as well buy a truck that has an LS in it, and scrap the one you have now.


Good luck. I guess California has "emissions referees" that decide your fate. You'd want to talk to one of them before you start making plans.

 

[slow_c1500]

Dang, that sounds like a lot of stuff I’d have to change over if I wanted to have my LS swap be legal.

The main reason I’d want an LS swap would be for reliability and fuel efficiency. Which brings me to a new question:

How could I make my 5.7 be as efficient as a non-AFM 4.8 LS? In terms of reliability, we have already discussed what needs to be done to a stock 5.7 vortec. I estimate I would gain 1-2 mpg if I did the swap, but maybe there’s a way I can keep my 5.7, not do the whole LS swap process, and have something just as efficient. Headers? Cold air intake?

I bring it up because maybe there’s a more cost effective way for me to get the benefits that I want from an LS swap.

 

[Schurkey]

The first thing you need to do is figure out California emissions regulations, and who the local "referees" are.

EVERYTHING you do to modify that vehicle has to be emissions-legal (CARB exemption number on every part, installed and adjusted exactly as specified. Or follow the OFFICIAL procedure for re-engining a vehicle.)

Good luck. What you want is going to be difficult if not totally impractical. Which is what they want. You're SUPPOSED to scrap the truck for something newer.

Tell your Governor "he's a dirtbag" for me.

 

[slow_c1500]

“Be grateful for where you live, some people have to live in California.”

Yeah the laws here are bullsh**. I am going to relocate after college. Laws aside, I still am wondering:

How could I make my L31 as efficient as a gen 3 4.8? If I decided to just mod what I have instead of doing the whole engine swap thing?

 

[L31MaxExpress]

I have never seen a 4.8L get good mileage and it has ZERO low-speed torque. My 99 Tahoe got 21 mpg highway with the 5.7L. My 97 5.7L Express got about 14 around town and 19 on the highway moving around a 6,200 lbs conversion van. 350/4L60E and 3.42 gears. If your 5.7L is getting bad mileage, I would start by fixing what is wrong with it or modifying your driving style. I could get single digit fuel economy in both the Tahoe and Van around town if I tried to.

 

[L31MaxExpress]

My first mod on the 350 was pulling the TB lip off the throttle body. It really helps the low-speed torque and throttle response. It lets you accelerate more briskly with less rpm and maintain speed better on the highway without the transmission unlocking the torque converter or kicking down to 3rd. Up to about 1/3 throttle if feels like you added 50 cubes to the 350 from all the added torque.

I believe JBA still makes Carb EO legal shorty headers. Definitely an improvement over the log manifolds. Finally I also believe the Volant air intake is EO legal as well. Research definitely needed.

 

[slow_c1500]

Ok, maybe we can disregard LS efficiency (or lack thereof). Would short or long tube headers or a cold air intake help out my 5.7 in terms of mpg?

 

[slow_c1500]

My first mod on the 350 was pulling the TB lip off the throttle body. It really helps the low-speed torque and throttle response. It lets you accelerate more briskly with less rpm and maintain speed better on the highway without the transmission unlocking the torque converter or kicking down to 3rd. Up to about 1/3 throttle if feels like you added 50 cubes to the 350 from all the added torque.

Already did the throttle lip mod, I like the jumpy throttle response