Engine knock

[2bits]

This is not truck related but engine related and you guys are some guru's so I hope it is ok to ask this question...

Last night I went over to my friend's house who has an all original 70 Nova with a 307, and it ran perfect when he parked it FIVE years ago... I was planning on buying the car. I changed the oil, put in a new battery, primed the engine oil before starting it, but when I started it, it knocks pretty bad from deep down in the middle somewhere and blows gray smoke. I couldn't get it to run good enough to drive it around the block, but I did drive up and down his long driveway. It just kept dying on me, I can deal with the running rough, it still has points which I didn't touch, and the smoking may still go away after running for a bit, but does anyone have any suggestions about the knock? I killed it and started it up a few times and ran it until the thermostat opened. Oil is not milky. I primed the engine by unplugging the coil and cranking it for 10 seconds then waiting 10 seconds then cranking for 10 sec and repeating that 7-8 times. Anything I can try to resolve this?