GeneralGrant

What kind of gas mileage can one expect with a zz4, what if i add tpi? are there other fuel injected build ups i can have done. My goal is a 350hp or so engine that gets decent gas mileage... My build up from last year, l48 bored .30 over highlift cam, 750 demon carb blah blah blah. gets like 11-12 miles to the gallon and doesnt have the ***** to excuse it. what do you think...

SanDiegoPaul

Ported injection is certainly more efficient than any carburetor. What is your budjet for this kind of project?

I too, am getting similar mileage with my 388 but I didn't really expect more. The combination I chose puts out a LOT of torque and the seat of the pants feeling is incredible compared with my OEM L-48 :yesnod: :lol: :)

Remember that it take TORQUE to move a heavy vehicle. :thumbs:

Not to get off the subject but my point is that if you choose the right cam and exhaust, a lot can be accomplished. As for mileage, and yes even performance, has the vehicle been Dyno Tuned since it was put in? It should be. Match the distributor curve scientifically to the carb jetting and the type of fuel you run. That can accomplish a lot! :seeya :chevy :hurray:

Ganey

Stock TPI is restrictive. Looks like you are over carbed for your setup. More data needed like cam & intake.

shotgun_000

If you want better gas mileage, consider an overdrive transmission. Many companies build beefed-up 200R4's that can handle 400hp or more. It has a lower first gear, plus overdrive. It will cost you the same as a good EFI system, but I think an overdrive will save you more on gas than EFI would.

Just my .02cents :cheers:

groovyjay

Have thought about Holley or Edelbrock EFI's? :steering:

theandies

I got 17mph with a Lars rebuilt q-jet a few months back driving from my parents in NC back to home in northern VA. Thats "normal" driving from me (read: not getting on it all the time, I love my 4 barrel). That is a stock ZZ4.
John

The Money Pit

I was still getting 17mpg with the 355 after 110,000 miles with the Edelbrock 1904 that I still run on the 406. Even now I average 15mpg. There's got to be a serious problem for a 350 to get only 12mpg.Vacuum leaks,burnt valves,hole in the gas tank,...........etc.I would estimate the 355 pushed around 320hp,and though was nothing to write home to Mom about,was no slouch.

shotgun_000

I have to disagree. I recently installed a new 350 engine, that now has about 2,000 miles on it. It replaced an 87' model 350 that had aluminum heads, and about 120,000 on it. Both engines average nearly the same gas mileage - 12mpg. I spared no expense in putting quality parts in my new engine, so I know that everything is in order with the engine.

The reason I get such lousy gas mileage is that I have a 3.70 gear ratio, with a TH350 automatic. Without even getting on the highway, 2500 rpms is fairly commonplace driving around. This is what causes my lousy gas mileage.

GeneralGrant, what gear ratio does your vette have? If it is close to 3.70, this is where your mileage is going.

Although things like new ignition, EFI, tune-up will help gas mileage, they can be only so effective when running a low gear ratio.

The Money Pit

I am running a 3.70 rear. When I baught the car it had 3.08's. When the posi went south I replaced the gearset with 3.70's and consistantly logged 17mpg. I drive 400 miles per week commuting to work.Some of the commute is twisty back roads as you see in my sig,about half is highway.Now with the 406 I've been logging 14.5 to 15 mpg. This is driving the car in a normal manner. When you open up the 795cfm carb,you can watch the gas guage slowly drop.

Ganey

PS Duals & headers increase gas milage.

I thought double digits was good. When the Corvette was relatively new, some guy w/ an economy car said to me something like nice car, bet the gas milage is terrible. I told him, it got great gas milage- I can almost get double digits.

:cool:

shotgun_000

Well, that shoots down my theory - back to the drawing board :(