A couple thoughts:
1) The exhaust sound of a Studebaker V8 is much louder than that of a Chevrolet V8, all else being equal.
2) The exhaust sound of an R3 is notably different than that of an R2.
3) Wouldn't the R4, with its two carbs, make a loud sucking sound when under full throttle? (I haven't had an R4, so no experience here.)
4) The supercharger of an R2 or R3 will make a nice scream when under full throttle.
5) The more horsepower an engine produces the louder its exhaust.
So, it depends on what kind of exhaust sound one wants.
--Dwight