Okay now I have a 1977 Caprice sedan with the 305 sbc (145 horsepower 20 mpg highighway)
I am planning on swappin a 2004 Cadillac esv lq9 into my chevy and going from EFI to carburetor along with a 700r4 trans and 3.42 rear end gears but first I want to know how much mpg will I get city/highway with about 345 horsepower I am also putting exhaust and cold air intake on my chevy and the carburetor is going to be either a quadrajet or a 625 cfm street demon. Thanks in advance

 

No easy answer for that question. To many variables to get a solid answer. A lot will depend on the weight of the car, The tune, Your driving style. It should have the potential to get 14-16 in town and 16-20 on the highway.

 

Don't take two steps forward to go three steps back. If you do your homework and shop for the parts second hand you can fuel inject it cheaper than carbureting it. MPG will be better and tuning will be effortless if you stay with a stock camshaft. The only advantage to a carb is that you can run it tuned crappy and never know it.

 

Go ahead and put wire rims and drum brakes all around while you're at it.

 

Can you share your thought process here on why you want to pull the factory fuel injection and go with a carb?

 

i thought about doing the carb'd ls for a sec while getting into my swap
i had lots of experience with carbs and they were in my comfort zone
all the wires and sensors were kinda intimidating.

i'm glad I held out though. This thing runs like a champ. Just getting my wick wet with HPtuners and it's a blast to change all my stuff around on a little laptop.

but if you do go carb, it'll be easy to tune it. even a pretty wicked hyd roller makes a really good vacuum signal to the carb compared to the olden days.

 

Congrats!

 

Well I am pulling the fuel injection because I was told that If I swap the lq9 then I will have to change the fuel injection and hey Im not rich lol but Is this statement true?.

 

If you get a complete LQ9 out of a vehicle it will come with all the fuel injection stuff. You will just have to have the wiring harness setup for the swap and do the fuel system for the fuel pump. It will be a little harder but fuel injection is so much nicer than a carb.

 

This belongs in the Conversions & Hybrids section, certainly not the internal (pistons, rods, cranks) section.

 

Stay fuel injection, if you do get a 6.0 and its the right years you can use all your current fuel injection setup. Ur mpg will more than likely drop with a 6.0 also.

 

Thanks for the info on the mpg... so what do you think would be the best engine for this car to get good mpg Im thinking about a 2004 5.3 or a vortec 1996 5.7 350

 

the 5.3 ls style over the old vortec any day of the week. much better power plant and better mpg. I would still get a 6.0 though as the mpg difference is minimal and you get more power. Get a whole swap from a truck with all the wiring and it becomes quite easy, and actually probably cheaper than going carb