I drove many Detroit powered trucks in various conditions , from highway to logging trucks in the bush . The 71 series like 671 and 8 v 71 even the twin 8v71 making v 16n's in the 50 ton rock trucks recommended rpm was 1700 to 2300 . I knew a guy that ran a 8v71 up to 2700 and never heard of him blowing it up . In logging form a 671 T I drove with a duplex trans with a flexible governor on serious grades required shifting only the main trans on steeper grades dropping 3 gears at a time in the prosses to keep it in the power band.
These motors were not like the current ones where a driver can get on a highway put it in cruise and let it go for a thousand miles without shifting .
At one point in the late 70's I was driving a truck with a 671 inline in eastern Canada and dropped and exhaust valve . I parked it on the side of a two lane road got a ride to a maw and paw truck stop ,spoke to the mechanic there who called his brother a local farmer who swung by with his John Deere ,towed the truck to the truck stop we dropped the trailer dragged the tractor to his farm stuck it in a barn ,gave me a room to sleep as I'd been up about 24 hours at this point and the farmer along with is brother over the course of that night replaced the valve along with the piston and sleeve in the damaged cylinder and I was on the road at noon the next day.
Yes they are noisy and leak oil and not all that powerful , but in the right hands they will go on forever .
John
