I had a 1600 cc CVCC 1977 Honda Accord in 1986 and I disabled 2 cylinders so it was 800cc. The gas mileage increased from 40 to 48 mpg, but it only had half the power (30 hp). It idled at twice the speed and I had to rev it much higher.
The Honda CVCC engines had a single overhead camshaft with rocker arms. I simply turned the rockers upside down on cylinders 1 and 4, and they acted as air springs. I drove it this way for about 200 miles, 150 highway. The car could not get out of it's own way, It was a struggle to get up to 55 mph. Semi trucks could out accelerate it.
I loved this car, it was great, but rusted out. Later I bought another and put in a 1355 CC engine with 10:1 compression ratio and it was 50 lbs lighter. I changed the 5th gear from a 75 civic and put on 185/80R15 tires. I got 50 MPG most of the time. It had a 13.5 gallon tank so it got 650 miles between fill ups.
HowStuffWorks "1977, 1978, 1979, 1980, 1981 Honda Accord"