Hello everyone, I am building a B18C engine now, CP 11.5 piston. I got a type r head recently, I've been told it has Ferrea over size intake valve. I'm planing running Skunk2 Pro2 cams. I have to set intake cam -8 degree, exhaust +8 degree to give intake and exhaust valves .040" clearance at vtec lobe 0 valve lash. I've done some research, most people with Skunk2 Pro2 camshaft set cam timing at intake -1~+1, exhaust +6~+5 degrees to have good valve to valve clearance. I believe that IN-8, EX+8 on my head is because of the over size intake valves. My question is that is there any limit that the cam timing can be advanced/retarded? I'm not sure if IN-8, EX+8 ok or not. Seems like 16 degrees out from factory spec is quiet big.

 

Hello, probably you can't get all out with those cams with IN-8, EX+8, if there is no play area because v2v clearance. I can say that valve events are not in the optimum position and you wouldn't make more power.
Best thing that you can do is to measure your actual v2v clearance with those cams so you know what are the real limits.

 

I've measured v2v clearance with the head on the bench.The result is IN-8, EX+8 to have .040" v2v clearance , so what ever cam timing I can play has to start from IN-8, EX+8. I'm wondering that 16 degrees is already too big. I feel that IN-8, EX+8 narrowed the overlap a lot.

 

Okay, then there is no much that you can do with those cams. It will work but not optimally, yes the overlap is very small and yet again your intake closes 8 degrees late so it bleeds out your dynamic compression that's not so ideal and exhaust valve probably opens too early and bleeds potential energy to the exhaust.
Sounds dramatic but these are the effects, so no maximum hp will be available.

 

Just read the document about these cams, it says do not use over sized valve. I have to change the plan now.