Even a model V8 doesn't sound truly like a full size. Usually the RPM are not the same and tone is different because of size. Each engine sounds different and this is due to intake and exhaust arrangements. Dodge V8's have a particular sound that is attributed to their exhaust header arrangement. A four cylinder running at twice the RPM of the full size V8, would theoretically have the same frequency, but still won't sound quite right.

I'll help you out with these links if you haven' found them online yet.

www.modeleniginenews.org

www.modelenginebuilder.com