[70KGOLD]

What kind of MPG did the 2 bbl 350s get in the early 70s? I have a 35 mile drive to work and I am thinking of building a engine to commute back and forth. Does anyone have a combo that gets 30 mpg of better is a older Pontiac car?

["QUICK-SILVER"]

Start with the highest torque at the lowest RPM engine possible. Don't use over a 390 cfm 4bbl. Get the tallest rear gears you can, like 241:1 and an overdrive transmission.

And it might be done.

[TIN TIGR]

get an early tempest with the 195 -4cyl..im working on 1 right now..gotta get over 30 ..it actually finally makes sense to build older cars now..you can get good mpg with mods..i know you can beat 20 mpg with a nice 350..the ohc 6 looks like it would be killer too..

[AG]

My '72 vert with a 350 2 bbl and 2.78 gear got 17-18 on the highway, not as much around town.

[smagnotti]

If any one could have got 30 mpg out of a 8 cylinder 350 they would have the worlds energy problem near solved!
May be you could could get 30 mpg out of a V8 if you do like some have done with a all aluminum SB chevy, and stuff in onto a motorcycle frame!

[TIN TIGR]

my old comet 289 got a solid 22 mpg hiway..my 194 -6 nova got 32..and i didnt have any cool tech like now..keep your car as light as possible, work on some aero..i bet a good 350 yak can break 20 without sweating..its a perfect small block engine..air up your tires, back off those drum brakes a little and loosen the wheel bearings a bit..make sure your rearend set-up is perfect with no drag on pinion..run a msd box and keep rpm under 3000..it will burn all the fuel..find an overdive trans that fits and lock up the converter manually..use the pontiac mantra, "tune for torque"..


im seeing a new game..who gets the best mileage, not most horsepower..then we go to most hp with mileage..who's in?...

[TransAm525]

What mileage are you looking for? If you are set on a V8, I would use the 350, set the rear end gearing up so the engine will be running at or near peak torque at your desired cruise speed, and use a small CFM 2-bbl carb. Other mods which would improve gas mileage are:

-Synthetic engine oil, ps fluid, transmission fluid, and differential fluid
-High output coil and/or multi-spark ignition box
-Advance the ignition for peak power
-Run the carb at stoich or slightly lean
-Reduce vehicle weight
-High flow air filter (less effort required by engine to pull in air)
-Headers and low restriction exhaust
-Roller cam and roller rockers
-Underdrive pulleys
-Install a shift kit and low stall converter (preferably a lock-up style)
-Tires set at factory psi (higher would increase mileage, but reduce tire footprint, thus reducing traction and increasing braking distances)
-Ensure brake shoes and pads have minimal drag
-Repack wheel bearings with synthetic grease
-Install electric fans or use a thermo fan clutch
-Run a 195 degree thermostat
-Use good driving habits (no rapid throttle changes)
-Lower car for reduced airflow underneath
-Polish and wax paint

Fuel injection is also another alternative, but it would take a few years to re-coupe the cost of the system.

[1967Clone]

Swap a cummins 4bt in it and you'll get 30 mpg.

[sleepy]

30 mpg with a 350 in an old car? That is a tuff one.
overdrive trans.
K@N filter.
fuel injection. tunable.
synthetic fluids. The thinnest you can get away with.
tall gears. 2.73 or higher.
loose as much weight as possible from the car.
High torque low rpm cam.
Headers and low restricted exhaust.
tall skinny tires.
lower the car.
and here is the big one. find gas that does NOT have ethanol in it.

[Overkillphil]

Definatly Sh--tcan the 2 barrel idea and put a qjet on it. The primaries are smaller and more efficient on the Qjet than the larger two barrel. And you have the huge secondaries for that odd time when you need it.

2 Barrels were for cost economy, not fuel economy.

[77birdman]

My 1977 350 with a 4bbl and a 2:41 rear end was getting around 25 mpg when it was new. What I hear the 4bbl is more fuel efficient than a 2 bbl, unless you step on it.

By the way I have 2 Qjets from a 1977 350 sitting in my garage. One of them is ready to go, works fine.

[loggerhead]

Pulled from one of my earlier posts:

TKO600 5-SPEED MPG "UPDATE"

--------------------------------------------------------------------------------

Original post appears below followed by "UPDATE".

1976 Trans Am
500 HP 462
Keisler/Tremec TKO600 5-Speed
3.23 Rear on stock wheels and tires
Rochester Q-Jet
E-Heads W/Performer RPM Intake
Comp Cams XR276HR W/1.65 Roller Rockers
Dougs Headers W/Pypes Dual Exhaust (no crossover), Dynomax Super Turbos
Weight had to be on high side of 4000 as we took car on vacation
with 2 adults, 2 kids, full trunk.

Atlanta to Chattanooga in 4th gear(1:1)= 16.5 MPG

Chattanooga to Atlanta in 5th gear(.64:1)= 22.66 MPG

I was a little rambunctious on the fist leg but the trip back was an
extremely restrained 70-75 MPH almost the whole way.

Car is still being tuned and I believe that these figures can be improved upon.
I don't know of a 6-Cylinder back in 1976 that got this kind of mileage.
Keep in mind this is not the first trip and these numbers have been achieved
more than once on the road. Any input on other combos and MPG's is
welcomed.

--------------------------------------------------------------------------
UPDATE:

I ran a measured course of 247 miles with the above combination. I recorded 22.4 MPG @ 60 MPH. I then swapped the 3.23 rear for a 2.41. I was hoping
to get close to 30 MPG. Instead, I got 24.8 MPG. However, I did run at
68 MPH instead of 60 MPH to avoid lugging the engine too much. Tach was
showing 1500 RPM which I think is a little high. My Tranny Calculator says
I should be turning about 1300 RPM. I think 25 MPG is obtainable at some other speed. My dad has a 2007 Buick Lucerne with a 198 HP 6 Cylinder
that only gets 25.5 MPG at 75 MPH. Folks, my car runs on a Rochester Q-Jet
with no computer control. It has 8 cylinders instead of 6, and 500HP. In otherwords, fuel efficiency could have been greatly improved upon in the
1970's with different gearing. I understand that not all cars back then had the necessary aerodynamics. Also, my results come under controlled circumstances and do not represent everyday driving. Bottom line...
while the rearend swap did help, it did so only to the tune of 2.4 MPG.

David

P.S.--- I have since determined by an O2 sensor that my carb could be leaned a little at
cruise. Also, I think my engine runs too cool due to it being roller cam
and rockers. I feel that with a little more tuning, and a hotter thermostsat, I could have gotten 25MPG and maybe more. Too late now as I have reinstalled 3.23 gears.

[PRC]

My first car back in 1979 was was a '72 Firebird which was totally stock with a 350 2bbl, auto, single exhaust, 2.73 gears. It got a measly 14 mpg on the highway! This was a pretty low-mileage (40K) well maintained car. I swapped a quadrajet onto it, had dual exhaust with glasspacks installed, a shift kit, and a good tune up and then it got 16 mpg. I never understood why these engines did not get better mileage. I think the Q-jet would definitely give you better mileage than a 2 bbl but the difference would not be huge.

By the way my '72 Olds 442 with a stock 350 4bbl , auto, dual exhuast and 2.73 gears has consistently given me 21 mpg on the highway for the past 26 years. Same size engine, heavier car, better mpg? The mpg with this car has always pleasantly surprised me.

[JACK_BURTON55]

My 76 Firebird Esprit, 354 2bbl gets 17 on the interstate pretty evenly. I really like the idea of a 354 that gets great economy. Should be to get at least 22mpg, im looking to get 20 with a Qjet upgrade and then shave some weight off my car.

Any ideas on weight saving areas?

[JohnTN]

My 1971 Olds 350 with 3.42 gears, 200R4 transmission, 27 inch tires, RV cam and QJet gets 17-18 mpg in surburan 4 lane driving and 19-20 at 60 mph on the interstate in a 3600 lb street rod. Overall mileage for 4500 miles is 18 mpg.

[69Customs]

350-4 barrel edelbrock, 1-1/2 wood spacer, tremec 3+1 overdrive poormans tremec, 2800 summit cam, 47 heads, mallory ignition at 12 degree (going to bump it up) headers,2-1/2 crossover exhaust, 3670 lb convert without driver, full tank gas, 2.78 posi., P255R60-15 in rear runs 20-24 highway 10-17 city depending on getting on it or starting in 2nd and shifting lightly in city. 2000 rpm at 70 mph, 16-17:1 A/F at cruise.
Fairly pleased with it but I think I can get a little more out of it.

[Will]

Even the most recent Trans Ams with their vastly superior aerodynamics, super low overdrive ratio transmissions, and computer controlled fuel injection didn't get 30 MPG on the freeway. They got close, I've heard reports of people eeking out 29 MPG while driving like granny. I'd think 25 MPG would be a possible with a car setup just right and the engine tuned to perfection. Otherwise, if you can get 20-22 at steady state freeway cruise speed I think that would be a reasonable expectation.

And you do not want the engine running at it's peak torque RPM on the freeway unless you've installed a cam that makes peak torque at 1600 or so RPM...

[Overkillphil]

Jack, the 76 has alot of areas you can improve as far as weight savings.

Shed the iron intake for a Performer.

Swap log manifolds for good quality 4 tube headers (@ 1-5/8" primaries).

Front bumper can be put on a diet, or replace with a 70-72 nose.

Replace rear bumper battering ram with one of those offered by a PY member in aluminum (forget the PY members name)

Remove some of the material from the door i-beams (swiss cheese it)

Remove A/C system if you don't need or use it, including the box on the firewall, replace box with American Graffitti unit.

Lighter and better brakes (rotors and calipers).

Lighter wheels and tires.

Fiberglass rear leafs.

Lighter exhaust system.

Remove heavy soundproofing and factory carpet, replace with modern adhesive soundproofing and new carpet.

Aluminum cylinder heads.

Aluminum driveshaft.

Fiberglass body parts (street grade).

Gym membership.

[JACK_BURTON55]

Thanks for the tips Overkillphil some great ideas but a few Q then back to topic! this MPG thing really interests me as my car is my driver to and from college and home.

ive taken some weight things off my front already but was looking into a fiberglass bumper part. Are the 70-73 fronts lighter by a large margin? or by how much?

I have seen those aluminum bumpers, great idea, and still functional?

door i-beams? where is this? inside the door itself??

How much weight can you save on brake parts?

looking into wheels that look retro and are light lol

are fiberglass leafs safe???

how much would an Aluminum driveshaft be??

go to the gym 4 days a week LOL

anything i didnt mention ive been looking into to try and save weight already. How much total do you think one should be able to shave off of a 76 bird? or any bird really?

[Formulafr]

i got near 17 on highway at 80mph. 350 4bbl (450cfm), 27" tire (on 18" wheels), 2.56 rear end, 3500lbs car, electric fan.


man, new cars here get near 50-55mpg. 60mpg on small last new cars