Can someone tell me is the valvetrain on the 2v aussie heads the same as the valvetrain on the 2v open chamber351c heads? Are the auusie heads a significant improvement over the 2v open chamber heads?Im interested in "street perfomance"
The difference between the heads is the combustion chamber size. The Aussie 2V heads have a "closed" (small) chamber where the US 2V have an "open" (large) combustion chamber. Changing to the Aussie heads will bump your compression ratio. The rocker arms are interchangable. Not sure if the valves are the same size or not, but I think so.
All 351C heads have a numeric cast into the corner of the head near the valve cover flange next to the intake. The numbers will either be a a "2" or a 4" --"2" indicates a 2V head and "4" denotes a 4V head. The only heads that do not have these casting numbers are the Boss 302 heads and the Autralian-cast 2V heads.
The Australian heads don't have smog bumps inside the exhaust ports and the Australian 302C heads also have a unique casting on the underside of the #2 exhaust port runner that begins with the letters "AR" (Ex: AR-D1AE). The "AR" is exclusive to the Australian heads.
They have 2.05" intake and 1.65" exhaust valves, and the intake ports are ~10% larger than the ports of the U.S.-produced 351C 2-barrel heads. The combustion chambers are 62cc's compared to the 351C's 2-barrel head's 76cc's.