STANDARD SINGLE exhaust size?? Trivial question.

[Valencia]

This awful exhaust is the main reason why there is around 20hp (maybe even more) difference between a HJ 5.0L with a single exhaust and the same car with a dual exhaust.

HQ and HJ dual systems (Holden V8) were pea-shooters and never 2" from factory.

Neither did V8 SLR 5000 Toranas