HKS Camshaft qestions

[ZzZleeper]

So i've been doing quite a bit of searching for the past couple weeks and cant seem to find the answer i am looking for!

The RB25 i purchased came with HKS Camshafts installed. I pulled the valve covers, and the Intake side camshaft is ingraved with RB20, and the VTC has been removed. I am trying to figure out what the specs on them actually are.

From what ive gathered, HKS offered 256 Intake, and 264 Exhaust camshafts for the RB25. And they had 264 Intake, and 256/264 Exhaust camshafts. Can anyone confirm this for me? I am guessing that the camshafts in my RB25 would be 264 Intake and 264 Exhaust camshafts. But i cant come up with a definitive answer.

If this is the case, and i do have 264 IN/EX i have also been told that it would require some head work and would need solid lifters to actually be compatible. Does anyone have any information on this? I really dont want to pull the heads completely apart right now to inspect it all for my self.

If anyone has any insight on this, it would be greatly appreciated! I dont know much about this subject!

Thanks!

[Skym]

Lobe height = lift

Lobe shape (smaller? base circle) = higher duration

I guess difference in base circle (or lobe shape), lobe height should give you a rough idea of the specs of cam.

When cam specialist regrinds stock cams, they adjust the base circle (make it smaller which I think increases duration) to get a little bit more hp from engine.

Head mods can include clearance mods to head itself (grinding head so lobes don't foul head) if lift is above a certain value (I think was 10.???mm lift on RB heads).

I think high ramp rate would affect hydraulic lifters and solid lifters are used if reving engine to higher rpm (from what I understand, hydraulic lifters can pump up and keep valves open a little bit at higher rpm) or have higher ramp rate with cams.

Also have valve springs to suit the solid cams, higher lift, higher rpm (also upgrade to bronze valve guides, as stock valve guides can crack at higher rpm / racetrack use or where heat levels are higher).

Best to ask a local cam specialist who are the experts.