Engine builders/Gurus, I need your help.

OLDSTYLE said
You could check to see if the timing chain or gears are hitting the block or cover somewhere. Also check alignment

I'll put that on the list.

Idaho said
I might be off base here, but just a thought. Would it be possible to measure the frequency of the tap, compare to rpm, and use that to narrow down the potential sources?

I dunno. I think that's a little over my head.

Purple Haze said
Just put the stock cam back in, no tap its the cam design. One more thing are those the recommended springs for that cam?

We think it's something to do with the cam, but not necessarily the camshaft itself. (Does that even make sense?)

The springs are box stock that come with 440source heads. Supposedly good to .600" lift.