Originally Posted by
James90RS
Chip,
No one seems to know what my head has had done
We think it is the following:
The ports just smoothed, and the throats opened a small amount
So Mark said go for the ported shroud
We do know it wasn't really much that has been done when you consider what you can do
How much would it lose you top end do you think?
I havent seen them tried back to back so cant give you an accurate figure mate.
If you want a guess maybe 10bhp or so less for the ported one on the same engine, but that really is only a guess from seeing other ported versus non ported not that specific one.
There are 3 differences between this and Rich's which add up to 40 odd bhp difference:
Headwork
Non ported shroud
Better intercooler
I suspect the surgeporting is the smaller of the effects if anything.