So last week i got to put several miles on my elky. Its 348/tri-power with 2 speed power glide, 3.08 rear. Now before everybody goes to yelling about don't worry about gas mileage, i don't . This is a fun car bought to enjoy. BUT! it got about 8 mpg.It is just running off of center carb for now. And the 2 speed shifts into high to fast. so it lugs a little. I now use the shifter to get it rolling in low a little longer. Any of you guys that have 348 tri-power. what kind of milage do you get with it? Just wondering?? And i use non ethanol high test. Any help!!
Don’t have any numbers, but growing up in the late fifties to early seventies, it was generally conceded that the 348 was a gas hog compared to its contemporary competition or its successor, the 327.
my 61 Impala has a 348 with 6x2's (only running the center 2) and a Th350 trans with a 3:36 rear gear. I have checked it several times on road trips at 22 mpg.....
Wow Moriarity, 22 mpg - that’s impressive. Here is a table from a road test of a ‘58 Impala from Hot Rod in that year; 12.9 mpg. Eight mpg seems pretty low.
Generally speaking the number of Carb's has little to do with Highway M.P.G. Stop and Go traffic your going to suffer if you get into the extra Carb's. Once out on the highway and at speed you should only be running on the Center carb. You should also be up around 12 mpg or better if everything is set up right. If you are braking in a new motor millage is going to be down a little but fuel fat is good on a new motor. 8 mpg,, you can improve on that quite a bit.
Dang, you must be climbing Lacon mountain and going back and doing it again and again! Seriously, I'd check the timing and spark advance. Sounds like it might be a bit low. Heck, my E350 motorhome with a 460 Ford got 8-10, depending on how hard you drove it and how hilly it was.
A rod going to the center carb to adjust shift point or is there a vacuum line going to the power glide, the shift point should be adjustable. Someone here with more knowledge than me on the old glides may know.
Lots of things to go through and make sure are happy like guys mentioned here. Are the outboard carbs set up correct with no idle circuits? Good tuneup on the motor? My 409 with the tri power set up gets better than that for sure although i haven't actually measured mileage. It's not a civic by any means but i like to get on the gas from time to time... Big believer in if the carbs are old, go through do a full rebuild, make sure all three are set up right. Baseline the motor and then sneak up on it from there. Lots of good info on 348-409.com
My 52' Chevy is my long haul ride. It has overdrive automatic with 3.23 rear and routinely gets 17.5mpg.
That is about the exact same setup we had in a 34 ford 5 window and was getting the about the same mileage.
Typical cars of that era got 10-15 mpg in town 348’s like 332-352 Fords were definitely not known for good mileage unless driven at 60 mph sustained speed. 8 is not good and what’s said above about looking at all the adjustments of the pg you should be shifting to high about 20 with light pressure on the go pedal and higher if you accelerate harder. Good luck
My 348 Tri-power gets around 14mpg on a trip (Imperial gallons) in a 61 full size Chev, TH700R. progressive linkage where the secondaries come in around 1/3 to 1/2 throttle. Not sure around town possibly 10-12mpg. US Gallon 3.8 litres (approx) Imperial Gallon 4.5 litres (approx)
Bruce, I had a 58 Impala with a 348 and a factory 3X2 set up that Chevrolet rated at 280 HP. The 2 end carburetors were vacuum operated. I don't remember the milage I got but know it was way better then your 8 MPG. Have you checked for vacuum leaks at the unused carburetors?
I have a 59 Impala HT with 348 - 3 x 2 set up, 3.70 rear and a 5-speed. overall is 15-17 mpg. As suggested previously check leakage on the end carbs.
Hello, Wow, 250 hp, 4 barrel, 3.36 gears and it is rated 12.9 mpg? At the time our 58 Chevy sedans came out, gas was $.25 to .30 cents per gallon. And the reply /was, who cared how much gas cost at the time, even for a limited budget teenager… When my brother bought his 58 Impala 280 hp 3 - two barrel 348 with a 3 speed, the rear gears were 4:11. He never took his gas mileage as no teenager had to think about such matters. Go somewhere, and when the tank was around a ¼ full, get some gas, (98-100 octane.) 1958 If the 348 200hp/3.36 gears got 12.9 mpg, our gas mileage at 280 hp 4:11 was way below that 12.9 mark. I can’t imagine what it was when one week went by using the 4:56 rear gears and then converted to the C&O Stick Hydro. (with as much street action going on during those days…) But, as stated above, who cared what the gas mileage was when gas was so inexpensive. That large 20 gallon tank just seemed to last forever. 58 Impala, 348 280 HP,, 4:11-4:56 GEARS, DAILY DRIVER Our high school was almost 3 miles away. Add in Bixby Knolls after school, then fill in the round trip back to our house on the Westside of Long Beach, was a total of 12 +/- miles a day. All stop and go city street driving was the primary route. When we did go down Coast Highway at faster freeway speeds on those long stretches, it was a pure, fun driving experience. But the daily costs were kept down with the “gas money” given to me by those I picked up on the way to high school. The gas mileage was much less than the stock 200 hp/auto trans version from the factory. But, it sure seemed like that 20 gallon gas tank lasted the whole week and then some. Jnaki It helped that we probably did put in more gas on Friday/Saturday nights at our weekly, cruising destination (Bixby Knolls) Texaco Gas Station. Our friend worked there and it was one of our stops on that nightly cruise. Of course, we paid for the gas, but it was all part of being on the scene. Whoa, if we still had the Impala, these days, less than 12.9 mpg is awful, with the price of gas. Since we do not do a lot of driving, other than our long distance, vacation road trips, gas mileage is not a factor. But, we have always looked at new cars or old ones that we knew got over 20 mpg in the city driving scene. Being carefree teenagers driving cool cars all over without a care or worry was pretty wonderful. It was true freedom that hot rods or family cars allowed teenagers to experience at age 15.5 or 16 years of age.
I owned a 58 Impala convertible back in the late 60's with a 348 tri power and a turbo glide. I got about 10 in town and 14-16 on the highway. Mostly at whatever the speed limit was plus 15 mph. When gas was 31 cents a gallon for premium who cared back then. You need some tuning on your Chevy. Sounds like late timing , also check your advance. adjust your linkage so it shifts at the proper speed. My uncle who was a service manager at a Chevy dealer back then had a 58 Belair 4 door with a 348 turbo glide with a 4 barrel and he would brag about his car getting 19 on the highway at 70mph.
That's the way I remember it too, same era. All said & done, tuned & tweaked, I'll bet that a little more gear would help matters too. Unless your moving to Kansas...
The Jalopy Journal
