Help with carb vs efi vs TBI

[Blue94sierra]

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?

I’m going to keep it as analog as I can, but I don’t have a 2nd vehicle so either way I’m screwed, so why not be screwed in style

 

[RDF1]

Do you have any experience in tuning a carb?

 

[Erik the Awful]

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.

Not true. Backpressure is never good.

Back in the '70s and earlier, the metal used in exhaust valves wasn't always as good, and if you ran an engine without an exhaust manifold bolted up you could suck a valve. I'm trying to google up a pic of a sucked valve, but not finding any. I've seen one - basically the face of the valve is stretched out into a cone. Back in those days backpressure was a necessity. In the '80s everybody started using better metal in their valves and sucking a valve stopped being an issue.

...but...

GM was using horrible crinkle-bent exhausts with tiny diameter pipes while everybody else started stepping up their exhaust sizes. Some engineer tried to explain it away by saying backpressure was necessary, when in reality the accountants demanded the cheaper pipe. All the hot car mags picked it up and ran with that disinformation for years without doing any dyno testing to see if it was true.

You can kill power by going from a restrictive exhaust to a free-flowing exhaust if your engine doesn't re-tune to it. If your buddy's cat back exhaust killed power, it was for show and sound, and not performance. Or his car didn't self-adjust to the better flowing exhaust.

 

[Drunkcanuk]

If backpressure was good.....the top fuel guys would have tiny exhaust. They are air pumps, any restriction is never good.

 

[L31MaxExpress]

People so often confuse scavenging with backpressure. Scavening is good, back pressure is bad.

 

[Blue94sierra]

Do you have any experience in tuning a carb?

Yes/no/partly. I know the basics just gotta try to learn again. Been a while

 

[1989GMCSIERRA]

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.

I had a 1988 454 K3500. Best I ever got was 9 mpg. Yiu shoidknhabe slightly more if you have a OD trans. If it’s TH400 it’s gonna be about where I was as far as mpg.

Seriously I would not swap the FI system. TBI is a solidly reliable simple and cheap to maintain system. It’s not a high Hp system but you’re driving a 7500 pound truck. I wouldn’t bother trying to “make it fast”

I would want it reliable. Tune up, fluids and filters. Drive it gently to keep the mpg up. I have vehicles that I drove for years with 200,000 plus miles and I learned maintenance and driving it normally is what pays you back.

 

[phantom 309]

i realize you don't have a big budget,. but if you can come across an old set 049's they'll raise the compression
look for some used headers instead of manifolds, as mentioned scavenging is key,. old 427 dump truck manifolds are good,. they work well for stock cast pieces,.
biggest fuel improvement would be a cam change,. blah blah,..