Help with carb vs efi vs TBI

[Blue94sierra]

hello, I’m new to the group but I read a lot on here, I’m trying to make my 94 Sierra k3500 more fuel efficient (I’m a comedian I know) it currently has a 454 TBI in it and is you’re typical dog. I know these aren’t race trucks but I want it to be able to hold its own. I also need to to manifolds on it which I’m open to ideas cause I live in the rust belt and the truck wasn’t taken care of by the previous owner. I’ll post a pic below for reference. But I’m looking for suggestions, tips, and directions on where to go on a sizably small budget.

 

[tpass]

It really is not worth any investment into new different fuel systems to try to get any better gas mileage from these trucks, especially a 454. The cost far outweighs the benefit.

The only thing is to keep it tuned up, keep tire pressures right and make use of a light right foot.

Why do you say you need manifolds?

Nice looking truck though and welcome to the forum!

 

[Komet]

The best way to increase mileage on a 454 is to keep it stock and give it a nice fresh tuneup with oem quality parts. Make sure your wheel bearings are greased, tire pressures set, brakes aren't dragging, etc. You can play setup games forever but big motors have a higher minimum fuel consumption and that's the way it is.

Or put a 350 in it I guess.

 

[Drunkcanuk]

Scallops!!!!!!!!!!

 

[Schurkey]

As said--there's no sense in changing the basic fuel system, the gains don't exceed the cost and aggravation of the swap.

SOME GM computer systems have "Highway Lean Cruise" mode that is disabled in the USA, but active on some export vehicles that don't have to meet NOx emissions limits. I don't know if a '94 has that option. Aside from computer tuning, and essential vehicle maintenance as already mentioned...Good Luck.

 

[RichLo]

Also with the addition of the above, free up the exhaust. A plugged cat and an undersized rusty hole-filled exhaust can really drag down efficiency.

Also check the spray pattern on the TBI injectors, if they both look the same and have a nice 'Christmas tree' pattern your good but if one is dripping or they look different from each other they need to be cleaned or replaced.

 

[Blue94sierra]

It really is not worth any investment into new different fuel systems to try to get any better gas mileage from these trucks, especially a 454. The cost far outweighs the benefit.

The only thing is to keep it tuned up, keep tire pressures right and make use of a light right foot.

Why do you say you need manifolds?

Nice looking truck though and welcome to the forum!

Thank you for the input, I need new manifolds cause I can see through them like a shotgun blast. Both ends of the down pipes fell so I held em in place till I can fix it. I welded them up a little to fix it till the summer till I can pull them. But I have a dynaflow and a magna flow welded under it and completely cut out the resonator and it’s a cat-less truck I’m also thinking about cutting a muffler out of it to see if it will do better or worse. I’m thinking fuel economy will be a little better cause of a drop in back pressure, just from those 2 mufflers being back to back.

 

[tpass]

Guess you mean your exhaust pipes are shot, not the cast iron manifolds that are bolted to the head?

Either way, exhaust back pressure can be funny, too little and you'll actually lose power. My buddy got a cat back "performance" exhaust on his Dodge hemi pickup and actually dropped a few horsepower. but that is just opening a can of worms and I am far from an expert.

JBA makes headers and Y pipes for our trucks and you can still probably source a stock replacement as well.

I personally bought the ebay/chinese $100 stainless headers and bolted on some universal Walker mufflers to my 1993 C3500 5.7L, but I was just looking to keep it reasonably quiet.

ETA I went the header route because I used a motor with vortec heads, hence the spacer on the tbi and a mechanical fuel pump. I had to use a carburator intake manifold. I wasnt sure if the stock exhaust manifolds would fit.. they probably would have.

 

[Blue94sierra]

Guess you mean your exhaust pipes are shot, not the cast iron manifolds that are bolted to the head?

Either way, exhaust back pressure can be funny, too little and you'll actually lose power. My buddy got a cat back "performance" exhaust on his Dodge hemi pickup and actually dropped a few horsepower. but that is just opening a can of worms and I am far from an expert.

JBA makes headers and Y pipes for our trucks and you can still probably source a stock replacement as well.

I personally bought the ebay/chinese $100 stainless headers and bolted on some universal Walker mufflers to my 1993 C3500 5.7L, but I was just looking to keep it reasonably quiet.

ETA I went the header route because I used a motor with vortec heads, hence the spacer on the tbi and a mechanical fuel pump. I had to use a carburator intake manifold. I wasnt sure if the stock exhaust manifolds would fit.. they probably would have.

Belive it or not it is the cast iron ones, the truck was beat to oblivion and back by my father, the first owner. And I am really trying to fix everything I can. I need the manifolds cause there shot, the gaskets to the block are shot and it leaks from the block end and the pipes. I really want to build the truck to how it was when I was a kid. I can tell you now it won’t be easy. And that’s a nice engine you got, if I liked small blocks I’d built one like it. And also there’s a dyna flow and a magna flow welded together that my father put in. And I want to cut one of them out since there right after another. And I never really saw the point of them being too close I’d rather space em out or only have one. It’s a single pipe so I don’t know how it would go backpressure wise. I know a little about it cause I’ve tinkered with stuff my whole life and by no means am I an expert but I like to think I know a little about a lot and a lot about nothin if you can relate

 

[RDF1]

Only drive it when you have to. Every dollar you put into trying to get better fuel mileage will take awhile to pay itself back if it picks up a couple MPG.
Plus going to a carb doesnt exactly mean better mileage. You going to install a wideband oxygen sensor to tune the carb?