Re: Aluminium GT40 \"Turbo Swirl\" Y-303 heads
Yes, they are. The intake and exhaust flow, especially at 0.400" and up, is more than 20% different if I recall correctly. The Ys are not cast any longer, as far as I know, they were a middle 90s casting from Ford. Shortly after the Ys came on the scene they were replaced with, I think as I'm going all off memory, the X castings which were quite a bit better and closer to what TFS, AFR, and others were offering.
The AFR Emission 185s won't pass? They have the air injection ports, if used, and pass smog tests all over America. I wonder what the spec levels are for what they are looking for in Australia? Europe emissions are actually easier to pass than the US emissions specs, despite Europeans all thinking the Americans are polluting bastards (we are, but our cars are cleaner actually).
Ron