power valve makes my 440 ping??

I'll agree with C130 on oil being sucked in the cylinders, something to look into, but most likely will show up on the plugs (somewhere), what i will question is the fuel pressure moving around, like i said earlier, you need to make sure its getting the proper fuel volume needed & maintane pressure, drifting from 5 lbs. to 9 lbs. is a "major" problem right there, you can't set your floats right if this is happening, so as you say, if left idleing it creaps to 8-9 lbs., where is it at 5 lbs., under excelleration?? If you set the float levels at idle & pressure is at 8-9 lbs., then its falling off to 5 lbs., your not getting anywhere like this, your float level is then dropping off from where you set it, the pressure needs to stay as "steady" as possible throughout the RPM range & "under load", another issue i see is the 1/2 fuel line & a mech. pump, 3/8" all the way should be plenty, unless you run an Elec. pump at the tank, then its easier to keep the 1/2 full, may not hurt to add an elec. pump at the tank, i think your Pressure will stay steady & you may notice no more pinging, plus you'll be surprized how much better its pulls. The larger your main line is, its harder for a mech. pump to keep it full vs. an elec.