Chrysler 426 HEMI displaced 426 cubic inches and produced 425 horsepower at 5,000 rpm and 490 foot-pounds of torque at 4,000 rpm. It had 10.28:1 compression and required the use of premium fuel. It used two four-barrel carburetors for air induction and cast iron exhaust manifolds. Fuel economy for the 426 HEMI was factory rated at approximately six miles per gallon.
.
My fun car in the mid ‘70s was a ‘64 dodge 440 coup with the 69/70 440 ci six-pack engine. I believe the compression was 11.5, but my memory may be foggy on that, but it would go from the Bay Area to Vegas without re-filling the tank, driving 80 MPH+ most of the way.
One trip I lost 2 rocker arms (on the same cylinder) and the car still made it to Vegas without re-filling.
.