symptoms of flattened cam?

[c20pickup]

what are the symptoms of a flattened cam lobe?

heres the backstory, ive got a freshly rebuilt 350 in my 70 c20. i had a local machine shop do the long block and i assembled the rest. the cam is a crane hydraulic flat tappet with matching lifters. i had the engine broken in at the machine shop in the chassis. it was ran between 2000-2200 for the 20 minutes. since the rebuild ive ran nothing but valvoline vr1 with a bottle of zinc additive. changed the oil after break in and repeated. the engine now has about 250 road miles on it and ran great until tonight. i was over visiting family and when i went to leave i got the old "do a burnout!!" so i whipped it around in the culdesac and went on my merry way. on the way home i noticed the engine was running rough and had an obvious misfire. after checking all the plug wires and all the obvious when i got home i also noticed a ticking/clicking noise coming from the valve train. so i pulled the cover and discovered the rocker on the intake valve for #5 cylinder had come loose and was no longer on the valve where it was supposed to be. the nut on the rocker arm didnt seem to back off because it had about the same threads showing from the stud as the rest of the rockers did. so i went through the procedure to reinstall and adjust the rocker. now to get the right adjustment on the valve the nut is almost bottomed out on the stud and has about twice the threads showing as the rest do. so i put it all back together and fired it up and still had the same ticking/clicking noise coming from the valve train. so in disappointment and disgust i slammed the hood and pulled it back into the garage. i should add that on the way home i noticed a plume of smoke coming from the left tailpipe, like a bluish white (maybe burning oil?) after taking off from an idle. any advice on what to look for or check next would be great!