Valve and Port Size for Engine Rebuild...

[Fly911]

I'm about to start to rebuild my '87 Carrera engine. The displacement will increase from 3.2L to 3.8L (GT3 crank, rods, oil pump, 102mm pistons, etc, etc). The cams are 325 degrees inlet and 318 degrees exhaust with high lift. The rockers will be modified to fit the cams. heads will be twin plugged. I'm already running Jenvey ITB's and Fabspeed headers, and a 997.2 GT3 muffler.

I will use the original cylinder heads, but with bigger ports and valves. I might go for titanium valves and springs. I need recommendations for valve and port sizes.

Any of the gurus in the Forum with good advise?

[Steve@Rennsport]

Hi,

While I won't comment about head porting, I would strongly recommend against titanium valves unless this is a full-on race engine and you are prepared to install beryllium-copper seats and steel lash pads. In short, a damned expensive proposition with somewhat short component lives.

[Tippy]

That is so bad@$$......GL with build and can't wait for results

[Fly911]

Thanks Steve, that is noted. What about sodium filled exhaust valves?

Any others on valve sizing and porting? 52mm inlet and 44mm exhaust...???

[gtc]

Might ask these guys:
Xtreme Cylinder Heads And Castings

[Steve@Rennsport]

Originally Posted by Fly911

Thanks Steve, that is noted. What about sodium filled exhaust valves?

Those are best for Turbo motors which see very high EGT's. These are heavy so we don't use them in race engines that will see 7500+ RPM.