There's plenty of little, common sense things you can do, like removing excess weight, proper tire inflation, polish the outside surfaces, but those old vans were terrible for gas mileage. Switching to a smaller engine like a 305 or 307 will help, but if you must use the 350, read on.
Use the lightest pistons, crank, and rods you can find. If you consult a cam manufacturer with your goals, they will suggest an appropriate cam for this application. An aftermarket intake manifold and small, 4 barrel carb or efi system will help. Also, headers and a free-flowing exhaust.
An overdrive transmission will also help.
Chevrolet Chevette was created in 1976.
145 if it has a 2 barrel, 165 with the 4 barrel.
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The power of the engine and the maximum speed of the 1976 Chevrolet Chevette Coupe are 70 hp and 55 mph respectively.
1976
Chevrolet used the 350 and 400 small blocks and the 454 big block.
9-13 if you lucky
About 10 to 14 mpg
In 1976, the average price for a barrel of crude oil was $13.10 (about $50.19 today).
The power of the engine and the maximum speed of the 1976 Pick-up Chevrolet K-20 are 103 hp and 65 mph respectively.
The 1975 Chevrolet K 20 has approximately 135 horsepower.
The 1976 Chevrolet C 10 ignition switch cylinder instructions can be found at most Chevrolet dealerships. The instructions can also be obtained from most auto-parts stores.