One hour, not me, but a guy an acquaintance hired to pull and replace the V8 in a 70's impala. I saw him start as I was walking up to my girlfriend's apartment and he told me about it. I thought yeah right, ya'll full of ****. An hour later I walked back out and saw the old engine laying on the ground in a tire and the car with replaced engine running. I was stunned to say the least. To this day I wonder how he did it, then again the dude was ripping around with his feet barely touching the ground.