So it seems that common opinion is that the rev 2 head requires modifying to accept high lift cams and in fact HKS etc typically provide a low lift & high lift variant to avoid the modification in the Rev 2 head.
My understanding was that the head requires the existing cam lobe cutouts in the head enlarged to provide additional clearance (I may be wrong - this is from memory)
From this pic you can clearly see the standard head grooves for above & below the bucket to provide clearance for the standard cam lobes.
My questions is: - Has anyone actually done this or had to do this? I have a rev 3 HKS 256 "High Lift" inlet cam (9.5mm lift) and they seem to drop straight in with no clearance issues. (what is sufficinet clearance? I'd estimate using my calibrated eyeball guage more than 1mm) Is there any other mods required that I have missed or got wrong?
(I will go shim under bucket or 1ZZ solid lifter to avoid shims flicking out)
The idea is to use the HKS Inlet cam and something like a rev 3 3sgte inlet cam on exhaust (240 deg duration and 8.7mm lift) or Rev 2 3SGE inlet on exhaust at 244 deg duration and 8.5mm lift to avoid running too much exhuast duration (overlap) and keep good spool up and on a Fraser McKellar mildly ported Rev 2 head I have.