Here is what ya do... Pull the motor tear it down and find out whats wrong, dont be a panzie dude. That definitly sounds like something internal.
Its not that hard/expensive to rebuild a B16... Unless you use aftermarket parts (Would be my sugestion since you will have it apart anyway) or something is sereously wrong. Like broken rods or something. I wouldnt be surpized if it had some aftermarket rods that were hitting the bottom of the cyl's, some people are retarded!