Symptoms of wrong cam installation

Keeping the compression up on a 340 with flat top pistons can be a challenge in itself with the cam that size I don't think you'd want your chambers any bigger than 55 to 60 cc and you mentioned ported heads that also are going to move the RPM range up .figure out what's going on with your camshaft but it seems like you have the parts to have a screamer if you get it dialed in jmo.