Which is why most HX V8's now have Edlebrock manifolds, Holley carbs, extractors and twin system fitted with some carefully hidden blocking of pollution hoses.

My HX Monaro had that exact set up on it when I bought it, and funnily enough so does the HJ Sandman I just bought.

The engine in the HJ is an IIQT HQ Statesman engine that has GEM engine rebuilt stickers on it. Appears it was a replacement engine early in the cars life..... Radiator was reconditioned in Mt Isa in 1978 and the Gem engine was fitted in Mt Isa so the original engine was probably cooked and cracked the block.