I have a 350 in a 70 malibu. The cam was shot rounded a lobe and the lifter wore a hole in the bottom, replaced the cam with a Lunati Voodoo. Nice cam. I have changed a number of cams on these motors. But now there is a knock. I even reopened the timing chain to ensure it was right buttoned it all up and the knock is still there. I checked the oil pressure normal, the torque converter good, even the flex plate was inspected. Re adjusted the valves (summit rollers) good. Could the rounded lobe on the old cam have hurt the piston?? please any advise is needed. The cam is a slight bit larger then to the old one.

did you flush out the engine after the wiped lobe to get all the bitty bits out? It's possible some slivers from the lobe got into the bearings. Is it a sharp metallic knock or more dull sounding?

dull sounding

I have a 350 in a 70 malibu. The cam was shot rounded a lobe and the lifter wore a hole in the bottom, replaced the cam with a Lunati Voodoo. Nice cam. I have changed a number of cams on these motors. But now there is a knock. I even reopened the timing chain to ensure it was right buttoned it all up and the knock is still there. I checked the oil pressure normal, the torque converter good, even the flex plate was inspected. Re adjusted the valves (summit rollers) good. Could the rounded lobe on the old cam have hurt the piston?? please any advise is needed. The cam is a slight bit larger then to the old one.
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Did you look at the bearings to see if anything was left of them??
Yes, a rounded lobe, especially one that bad circulated crap everywhere in the engine & it could have done a lot of damage.
It is never a good idea to replace a cam with a lot of metal missing without cleaning out the engine & this involves more than giving it an enema :D
The metal went somewhere,,,,
And yes, you can still have decent oil pressure with ugly bearings,,