350 motor need help

I have a Chevy 350 motor that I just built and put in my truck. I had it running pretty good and drove into town when it started sounding like it was starting to misfire. I pulled in the parts store and when I got back in it the motor cranked slow but did start. The whole way home it sounded like one of the cylinders was not firing at all. I thought if I pulled off one plug wire at a time and listen to motor change in idle I would find my dead cylinder because the idle wouldn't change when I pulled off the wire of the dead cylinder,right? Well, I pulled off about 4 different wires and never could hear a difference.

The motor has a 240 cam, dual-plane aluminum intake, a 50,000 volt coil on the HEI distributor and everything else in the motor is stock size parts.

Any help and suggestions would be appreciated.

could you have possibly forgotten to tighten the distributer retaining bolt after setting the timing or could it have come loose? also did you break in your cam properly, did you adjust your lifters properly as well...... lots of possibilities when an enging is rebuilt. One thing i will say , it almost sounds like a timing problem, once it gets warm and if the timing is out it will be hard to turn over.

I did find that the distributor bolt was loose. I didn't follow any specific break in procedures for the cam nor did I have a degree wheel to dial it in, so the marks on the timing chain where lined up and that was it. When I adjusted the lifters I backed the rocker nut off (while engine was running) until I heard the rocker tap, waited a second, then tightened until it got quiet and then another 3/4 turn.

Even though the cam isn't too far from stock is it possible that lining up the marks still set the cam too far advance?

The correct timing setting would also be helpful. I heard 8 degrees BTDC. Is this right?