I have a 1978 f250 with a 400 in it, lots of miles not pretty but has been a dependable truck. My wife was driving it hit a bump and it died and wouldnt start, no spark to plugs so I tested the coil and ICM and there both good. Went looking at the distributor and walla when cranking the rotor wasn't turning
. So obviously I pulled the distributor as its the easiest,check the gear and its on tight roll pin firmly anchored altho it feels like theres some play between the top and bottom of the shaft (not sure if this is normal) almost springy feeling but only an 1/8th of an inch play. Flashlight down the distributor hole the camshaft is turning, valve covers off all valves opening and closing. Put distributor back in, crank vehicle rotor doesn't turn , distributor shaft doesn't turn rockers move opening valves
. Take distributor back out turn motor over several times while watching cam gear no broken teeth no unusual wear on the gears not metal shavings nothing. Any ideas or help would me greatly appreciated.