How low is to low?? I think the engine will let you know. It will depend on the cam , comp and cubes and weight.

If I remember correctly my 5.4/330 CI motor F150 cruises at about 1800 to 2000 RPM with 3.31 gearing at 65 MPH Its fine on the flat and mild grades before it needs to down shift.

A 440 CI motor set up similer should be able to cruise at even a lower RPM. But, Like I said, the engine as set up will let you know.


As far as motor Efficiency goes. They are most efficient per CI at there max torque RPM.

The Problem with that.

Is that these cars are Grossly overpowered. At Max torque you could be making 500# plus easy on a near stock 440. Burning All kinds of fuel in its efficent max torque rpm.

Again the problem,

We need very little torque compared to what these engine can produce to say, Cruise at 65 MPH

So with a resticted throttle the engine itself may be in a less efficient per CI, it is in a Far more efficient state in reguards to fuel consumption.


A restricted throttle reduces volumetric efficiency per CI, making it run like a Smaller motor. Technically if the fuel to air ratio stays inline, and it does. The motor isnt in efficient at all. It just runs like a fuel efficient smaller motor. mike