Carb vs. Injection ... Which gives better mileage on 5.7 V8?
 

I am about to buy Chevy Blazer K5 SUV 1988 with 5.7 L V8 carburetor engine with low mileage mostly garaged.. will conversion to fuel injection increase its mileage?.. The owner says it came originally with diesel engine and replaced it with original new 5.7 L V8 in 1989 and has genuine 42000 miles on it

Will conversion to fuel injection help increase its mileage and travel range? Are there any other options available for this engine for improving its mileage on highway and city driving and extreme off road driving

Fuel injection will provide an increase in mileage over a carb. How much depends on how out of adjustment the carb was to begin with. If you know what you're doing, and take your time, you can tune a carb to get pretty dang close to fuel injection, especially with a quadrajet. Something like an air-fuel ratio meter would drastically help with tuning a carb.

modern fuel injection is pretty reliable, but since you mentioned extreme off roading, all those fancy electronics are just more things that can fail. Especially during river crossings!

i tell ya,quads are the best carbs for fuel economy,but can be a royal pita to get it tuned right. thats why alot of people hate em. i like them.

Can you suggest any easy equipment which i can use to tune the carb? as i am not a mechanic and prefer doing it myself if its easy ... Would you also please suggest any easy to use air-fuel ratio meter

Fuel injection is better for off-roading. QuadraJets are good off road, but still flood the engine on high angles and big bumps.

Are there any solutions for preventing flooding of engine on high angles and big bumps

Not really, over the years I've tries Carter AFB with off-road needle and seat, that worked OK. The Truck Avenger was about the same, just OK. The QuadraJet with the float bowl set low was the best 4 barrel I've tried. The best off-road carb I've run so far is the 2 BBL Motorcraft 2150.

while I don't have any direct first hand experience with them, I did do a little research a few years ago when I was thinking about putting one in my 73 chevelle to aid in tuning. All it really consists of is welding a bung for an 02 sensor in the exhaust stream, and running it to a gauge you have mounted in the cabin. Check out summitracing.com for some. They're a little bit more expensive now than I remember them being.

Converting it back to Diesel would be the best MPG option...

Depending on what state your in if you take it in for inspection they might not like seeing a carburetor on a 1988 model that was originally a 6.2...

If it runs good now and you're getting at least 12mpg combined 15 on the highway I'd leave it as is. You can spend a ton of money putting fuel injection onto a vehicle and it just won't pay off for you.

Unless you're handy under the hood and able to refurbish junkyard parts I'd expect to spend about a grand to swap an EFI system under the hood. Best case you'll pick up a few MPG, lets say 3 overall which is very optimistic. We've got $3.40/unleaded out here and assuming you drive the average 10K miles a year that means that you're fuel cost at 12mpg combined for a year is $2,833.30. Now if you bump it up to 15mpg your annual fuel cost is $2,266.60. You saved $566 in a year.

If you only drive 5,000 miles a year you're now saving about $250. If the actual change in mileage is only 1.5mpg and you drive 5,000/year you've saved yourself less than $150/year in fuel by spending well over a grand.

If you're really concerned with mpg then you're driving the wrong vehicle, go get a Yugo or LeCar. Sometimes the best way to save money is to do nothing.

I will drive 22K per year so I am OK with 15 mpg on highway and i agree its not worth the hassle to get an additional 3 mpg so i will settle for carb.

However i need offroading solution for carb without effecting the highway mileage of 15 mpg as 30% of this will be used for extreme offroading terrain driving through various tilts and angles at sea level and even at places as high as 15000 feet at times with change of temperatures as one drives up the steep hills so need off roading solution to avoid flooding or fuel stoppage