Help needed just bought. a 93 c 2500 suburban with a Tbi 454. Looking to improve low end performance and of course g a s mileage.in the 80s I did this with a carb setup. Rv cam small carb intake and headers. but Tbi is new to me .should I revert to the old setup or and cam intake and headers designed for the Tbi .any thoughts on which would give better mileage. Thx

 

There's a local guy to me that has a 454 in his square body suburban. He converted to the Holley Sniper FI setup (which is similar to TBI). He's been very happy with it and says it's worth every penny.

 

Thx .I would like to know if he got better gas mileage than with the carb.

 

The problem with the factory TBI stuff is it's now ancient and even back in the heyday was limited to what it can handle and do. You could check out some of the 454SS truck websites and find guys that still burn chips for it. You would honestly be better off with a more modern injection system and not use the pocket calculator computer the truck has currently if you want to make your fueling as efficient as it can be along with headers and cam changes.

Compression is efficiency though and the dismal 7.8:1 those engines have is pretty counter productive.

 

I don't really have his info to quantify an MPG improvement, but the tune-ability is there to make adjustments for different throttle and RPM scenarios. I have read that out of the box they're set up to run on the rich side--for liability's sake. Outside of MPG, the effect was a lot more refinement, great throttle response, and an overall better driving experience. With some tweaks to fuel and timing tables with an eye on A/F ratio during some street driving you can achieve those claimed MPG results, but I wouldn't expect it to be perfect straight out of the box as every setup needs some custom calibration.

The other difference was that he was running a TH400 until he recently upgraded to a 4L80e. The lockup trans will give the biggest impact, but being that you have a '93 you're already ahead of the game.

What kind of MPG are you getting now?
Converting from TBI to Sniper EFI would probably not be worth the expense unless you really want the adjustability.

Here's a helpful article from a guy who converted from carb:
https://www.chevyhardcore.com/news/sniper-efi-update/

 

Lock up and overdrive

Are you talking about the guy who runs the Square Body Brothers instagram page?

 

Thx for your answers. I'll post my results when I finish modifications. Being an old-timer with n minimum efi knowledge I'll probably go with the old carb setup I am familiar with.

 

That's the one.

 

I understand the apprehension to dive into something new, but they've really taken the guesswork out of it.
Personally, I'd rather use this little handheld tuner with actual readings than a timing light, a flathead, and some guesswork.
Dollar for dollar, it's really not more expensive either if you're buying new parts (intake manifold & carb)..