What is the best flowing stock head for our engine? I know we have VCT but is it worth eliminating, or is it not enough of a gain? I as thinking of swaping to a Focus head.
the svt focus head flows better i believe, but that’s not by much i don’t believe. used right vct can increas power by a few ponies, but not anything drastic. I’m planning on porting a focus head and using crower cams in my build.
the svt focus is the best flowing head (straighter ports, longer valve springs and valves allowing higher lift cams) but does create a few real issues when trying to install on a zx2 (bolt pattern of zx2 manifolds match but not port shapes, vct on intake side needs to be bushed and disabled)
as for focus and zx2 heads, they both flow similar and not enough to call one a better swap from a flow perspective. the focus head loses the vct of course and thats the attraction for lots of builders
but the zx2 head is plenty good on its own… 90 percent of hp improvement comes from just the cams and head milling so all the additional work for another 5-10hp or so is not worth the extra hassle imo.