Safe cruising RPM is something I have wondered lately as well, since I am about to install a fresh rebuilt 261 into my 53 1/2 ton. I was curious to the max cruise speed that these engines can handle. I figured 55-60 mph would put the engine in the 2,500-3,000 rpm range, which might be a fast as I would comfortably run one for a 10+ mile trip. My truck is stock configuration and the furthest trip I ever foresee making in it is a one-way highway trip of about 85 miles. I know "in theory" my truck will run up past 80 mph and 5,000 rpms if pushed to the max, but at what RPM do these engines enter the "danger zone" pertaining to lubrication, etc when run for an extended period of time?
Last edited by Green_98; 02/14/2019 7:07 PM.
