OK, I just went out and started it, a 95 4.0. It was 27 outside, I started it and let it warm up, setting the fan on the second position of three until I got up to temp. It took about 10 minutes to get up to full temp at which point it was putting out good heat. I was tacking about 4.5 rpm fully warm, it was just under the imaginary #5 between zero and ten. It sounded like it was in its fully warm 'sweet spot' at idle, just right. And no.... my unit doesn't have a pin at the bottom of the tachometer sweep. I have 145K on the motor with a fresh oil change 10w30 and Rislone 'Zink' treatment.