The Stovebolt Site Forums The Shop Area Engine Shop Upgrades for fuel economy

I have a 265 V8 with a Rochester 2 barrel carb.Is in a 1956 3100.As far as I'm aware everything is original.What upgrads should I consider to get better fuel economy.Thankyou.

Buy a Japanese 4 cylinder roller skate for a daily driver and drive the truck on weekends.
Jerry

Tune the engine and perform general maintenance to start with. Install an overdrive transmission which will reduce engine RPM's and provide better overall performance.

Fred

If this is a metering-rod controlled carb, measure/record the rod diameters (probably 2) and jet sizes, Go down 1 jet size (may not be safe for WOT) and test for engine vacuum at a specific cruising speed. If this helps (vacuum goes up), you want a rod pair with the same effective "economy step" area (jet ID squared - rod OD squared) and probably the same jet size. This will lean out only the cruising mixture.
Are you sure your vacuum advance can is working?
Some more ideas on my web page here: http://victorylibrary.com/mopar/mileage.htm

Check this link also:

http://www.thecarburetorshop.com/Troubleshooting.htm#Fueleconomy

Jon.

Stooby,

In 1957, when I was a 13 year old kid, my parents bought a new 1957 Chevy station wagon equipped with a 265 engine and a "Turboglide" transmission. Even at age 13 that car was instantly recognizable as a future classic, the last of the "Shoebox" era. They had that car for about 10 years until it was hit by a drunk driver and badly damaged. The best fuel economy it ever got was about 14 MPG, and that was on good gasoline with no ethanol. The 265 was a very wimpy engine, way too weak for a family and camping gear.

I still remember having to get out and walk the last approximately 1/2 mile to a lake at elevation approximately 10,000 feet in the Sierra Nevada mountains in California. The wagon simply couldn't climb the last bit of that steep grade until a few hundred pounds were offloaded. That few hundred pounds was my friend and I.

Based on that I'd guess that a 265 can be counted on to deliver both poor fuel economy and weak performance.

Engines of that era were designed with not much thought towards fuel economy as gas was 25 cents a gallon. Here is what I did on my 37 Buick with a straight 8 that clicked out a steady 12.5 to 13 mpg. First a complete tune up with the car on the chassis dyno and O2 sensor in tail pipe. Got it at maximum power and torque which I knew would NOT be maximum economy but gave a point to work from. Then cleaned up the air resistance by removing the sun visor, outside mirrors, trip lights, bumper guards, radio antenna, but did leave the aerodynamic hood ornament. Put on radial tires with psi of 40, replaced all fluids with Torco synthetic, installed a 190 degree T-stat, and replaced mechanical fan with electric. Retained single exhaust with free flowing muffler but your V8 would benefit a little bit with duals. I tried different gear combos and did some "seat of the pants" tuning all of which resulted in a 2 to 2.5 gain in mpg. Gas was near $4 at the time and I was going to be the first one with a 20mpg straight 8---dream on. Car is back to normal now and so am I. Weight, shape, engine air flow efficiency, and piston travel in feet per minute will determine economy and your truck is hurting in three out of the four so don't expect the moon.

Observed many "won't make it" events on hills etc. over the last 60 years. Two major reasons:
1. the driver won't downshift
2. the driver is afraid of full throttle

I remember getting an increase of 10 percent better mileage in my '82 Mazda pickup by switching from Dino oil to synthetic. This was done when the truck had not many miles on it.

I certainly am not an expert as to whether this would be a good idea for the older Chevy engines or not.

I also picked up 1mpg by adding a homemade air dam under the front bumper to scoot the air out to the sides rather than having it compress under the truck.

Cheers, Dean

I had someone tell me that driving with the tailgate down would also gain 1 or 2 mpg.

Not sure on that one. It "could" be the case on our older trucks, but I've seen several smoke streams from the labs studying air flow in a wind tunnel and modern trucks lose mileage with the tailgate down or off. It messes up the factory aerodynamics bigtime. On a personal note, my wife's truck when new (2015 Ram 2500 4x4) got a dependable 17 to 19 mpg. When it was about three weeks old we pulled the bed and installed a new CM flat bed. No tailgate obviously and a small bit, around 2" or 3 of headrack and flatbed extending past the cab. With the flatbed induced airstream disruption, mileage dropped 2 mpg and now runs 15 to 17mpg on a good trip when not pulling a trailer.

I think coilover was on the right track in his chasing 20mpg with a straight 8. Now I'm just dreaming here and odds are likely never will, But if I wanted to build a mileage champ AD truck, I'd go diesel. Not Cummins, though I'm a Cummins fan but a Isuzu 4BD1TE. Thisdetails a Isuzu conversion on a Toyota Landcruiser that was seeing 26mpg. Not Stovebolt but interesting for sure.

All the above said, mid teens ain't bad for our rigs. I've got better on long drives but fact is these trucks aren't about modern mpg. For me it's more about spm (smiles per mile) than mpg.

I had someone tell me that driving with the tailgate down would also gain 1 or 2 mpg.
Mythbusters did this, and in their test it hurt: http://www.discovery.com/tv-shows/m...abase/driving-tailgate-fuel-consumption/

All tests that I have seen dropping the tailgate hurt the mileage.

On the other hand, a cab-high aluminum bed topper seems to help the mileage.

Personally, the two largest gains I made on my own 1968:

(1) Switch from a dogmatic to a 4-speed (24 percent)
(2) Removal of the "bug screen along the front of the hood (12 percent)

Jon

Carbking, I'd be interested in the details on your 68. I'm also working on a 68 gmc. My first mileage check was 15.25 but I found that the choke was not opening completely so I'm hoping to do better on the next tank. I have a 292 with 390 holly 4 bbl and HEI. All the internals of the engine are stock. I have an A833 OD transmission and 3.73 rear gears. It runs about 2000 rpms at 60 mph.

Not a GM - it might be frowned upon if I posted exact details on this forum

But it is a half-ton, with a V-8 somewhat smaller than 400 CID with two Carter 625 CFM carbs running solid linkage producing approximately 450 HP and a 4-speed with granny low.

Will pull from idle to WOT with zero hesitation in 1st, 2nd, and 3rd. Will pull from 1100 to WOT in 4th.

Jon.