Turbo Cylinder Head Question

Road Weazel

Or, "Hey look, it's the new kid again..."

So, here's where I'm at. If you've seen my previous posts, I was trying to figure out which direction to go with my Stage 1 Hahn Turbo'd Hayabusa. I pulled the motor after my turbo rebuilder told me that he found some melted aluminum on my exhaust veins, and that there was some very slight damage to one of the blades. With the head off my problem was easy to see, because the rings were easy to see. At least I already had the Wossner pistons in hand, and my cylinders are fine.
I'm going to upgrade the engine with the Wossner pistons, APE cylinder studs, main bearing studs, valve springs, cam sprockets, OEM cam chain and tensioner and rod bearings. There may be more, I still haven't pulled the valves from the head.
I will have a light porting job done on the head while it's off and have the seats re-cut to a multi-angle with radius using a Serdi machine. I don't want to get too stupid with the porting because this is primarily a streetbike, and I want to maintain good driveability. Corky Bell didn't have much to say about porting head, except to say that with increased boost smaller imperfections behave like bigger imperfections.
My main question lies with the exhaust side of the head. Would there be any real benefit to installing 1mm oversized exhaust valves in a turbo head? The valves themselves (Kibblewhite) are the same price either way. Also (OK, that makes this two questions), when porting would it make sense to open the exhaust ports by a fair amount or just clean them up? I'm thinking just clean them up, but I wanted to ask.
Any other suggestions, aside from "Go suck carbon monoxide, Kid" would be welcomed.


Don't waste your money on O/S exh. valves, just get a good valve job put it by together and ride! You won't see no gain in power with a hahn set-up with O/S valves that for racing with real turbo kits!
Stock head, stock valves, APE (or similar) springs, stock cams (degreed), Wossner pistons, .080 spacer, wossner rods, studs, and a gasket and you'll be good to 500+hp....IF you fix your issue. Otherwise, you will melt the pistons just like you did this time.