340 issue after camshaft change
At this point, it’s very probable the grind is not right.
IMHO, you need to get to the bottom of the problem. To do that requires degreeing the cam. You do not need to remove the head to find true TDC. A small screw driver or bit of coat hanger or welding rod will let you feel the piston come to the top and start to drop. Back up a few degrees and install the degree wheel. A piston stop can be made by grinding or cutting the crimp that holds the porceline in and push it out. Weld a nut on to use the largest diameter redi rod that fits through the plug body. Grind one end of the redi rod round and then cut it off about 3" to 4" long. Loctite a nut on the cut end to turn.
Now you can install the body in the #1 plug hole and thread the piston stop rod in until it just touchs the piston crown. Back it out one turn and roate the engine about 30° to 40° ATDC. Turn the piston stop down about 3 turns. Now you can back up the rotation until slight resistance is felt. Note the degree indicated. Now rotate in the normal direction until you feel the slight resistance again and note the degree reading. Now pull the stop out and rotate to half way between the two noted degrees and move the zero mark to line up. Just to be certain at this point I would go to 40° ATDC again and install the piston stop. Now check your ATDC and BTDC degrees. They should be identical. Now you can check timing per the cam card supplied with the cam.
There could be an error with the cam grind with regard to the relation to the keyway or a key slot in a timing gear could be off. With #1piston at true TDC the crank timing gear dot should be straight up and the cam gear dotright opposite. You know this. #1 or #6 should have both lifters raised a slight bit with the other on the base circle compression. If not, one part is likely machined wrong.
At this point you likely will remove the timing set to get at the cam. Try it on another engine. Maybe someone close has an engine apart or a spare. This will verify the timing set which is way less expensive than a cam. If it is the problem and you purchase another cam and heave the one you just took out 10' into the scape heap, you could still have the problem.
Realising that most companies unfortunately have stuff manufactured in the land of recycled Yak turds means either the company or the customer needs to have a QA/QC program to ensure quality.