IDK about 400, thinking of what Landy did back in the day with those monster rectangle/square ports. But for all sanity purposes, by the time you carve away what’s needed for that kind of flow, I would not expect much life from the cylinder head or reliability.
I was hoping for a little better out of W5’s myself but it gave up the ghost on that in one port. Not that it isn’t flow well as it is now. But more the merry and the planned 434+ mill can use everything it can on a cylinder head.
I agree stepping up would be it. W7-8-9…..
@justinp61 arent you running a set of Indy heads on your mill?
