Fired up rebuilt 318 for break in. oil pump primed, carb fuel bowls filled, timing set. Using pertronix ignition conversion that worked on previous engine. Ballast resistor replaced with wire per instructions. Engine turned over a couple of times and fired right up. Ran to 2000 rpm for cam break in. Had to stop after 10 min for oil leak and had forgotten to tighten distributor clamp down and had to replace alternator because of bad bearing. Had to wait a few days for alternator. Fired it up the next week to finish break in. Started right up but after about 5 min, again at 2000 rpm, the engine started losing rpm, then running rough, and died. Engine would start back up but run extremely rough then die. Now won't start at all. Am getting fuel but apparently no spark. Replaced distributor cap because the graphite button in the top that contacts the rotor was broken. Made no difference. I pulled a spark plug , plugged it into it's wire and cranked engine. No spark. Where do I go from here? Not good with electrical at all. Thanks for any help.