Ok my update is i now have a billet custom grind turbo cam from surecam and valve springs to suit, my question is can i use a Au steel Head gasket either side of a acl copper head gasket to lower compression?

Oh yeah i blew my t5 up after beating a 380hp r33 skyline and i now have a g-force upgraded gearbox coming over from the usa with a strengthened t5 housing.

how much that gearbox setting you back?

yer and what sort of power should they take? use the same clutch?

I'de be interested to see the cam specs, pm me if you don't want to post them on here for what ever reason. I've just recieved a custom billet cam from surecam for turbo application too and I wouldn't mind finding out if the grind is just a generic or if he listened to everything I wanted and worked out a custom cam. What valve springs have you been sent, I've ordered double valve springs with matching spring cups collets and retainers from crow which I'm picking up on monday.

Not sure about the headgaskets either side of the acl copper gasket I'm pretty sure you will have all sorts of sealing problems. I'm having 5cc or so removed from the combustion chamber and probably using two of the AU style gaskets which makes the same thickness as one of the old carbon style gaskets.

I can't remember exactly what the combustion volume is but its around 76cc?? (corrections please if thats wrong) so by my calculations removing 5cc of metal from the chamber lowers the compression of a standard 9.35:1 falcon to 8.8:1 which should be enough to run 18psi or so safely