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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.
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34 mpg? Really ...