When I put it in gear and hold my foot on the brake and push on the gas, that is when I can hear the valves rattling as I call it, or real bad detonation.
The weird thing is it does not blow any smoke from either tail pipe. The last time when my cam went flat in my last engine it was blowing smoke like a train and idling very rough.
When it is idling it runs fine and you can blip the throttle and it doesn't sound like there is any mechanical issues.
Thats one of the disadvantages to a lopey cam. Sometimes its hard to diagnose if you have a ignition, vacumn leak or what is wrong.