Originally Posted by
pa_sjo
Completely different heads. The only thing remotely similar is the size and shape of the exhaust ports.
If that was true then you wouldn't be able to easily swap a ST170 head onto a 'blacktop' engine.
The
detail of the valves, cams, etc. are different as it has high lift cams and, as mentioned, the VVT on the inlet cam. The inlet port is bigger and flows a lot better than the shape of the standard/RS head, but the valve sizes (but not stem lengths), angles, cam centre lines, etc, etc. are the same as the standard/RS blacktop.
Oh, and even the head chamber volume is the same......
Martin