rap rap, not
wrap wrap?
From the experts on producing such noises. 
All I know is that my 261, with many carburetor setups and two different dual pipe/exhaust setups, made/makes too much noise.
Enough that a police officer pulled me over and told me that he had called me in because my rapping made him fearful that I would try to run him (I asked him if he would please write that on the ticket/summons).
Gleaned from the link above: if you are using original diameter pipes, you should expect reduced "rapping".
The 216 engine might also have only minimal rapping potential?
