1NZ port & polish

[Dragonacc]

Originally Posted by Galavoxx

I don't entirely agree with that. OF course a higher redline is going to showcase the potential of larger valves. However, with a flow bench designed head and larger valves, the hp should be avilable everywhere, not just up high. I'm not saying that the 1NZ has the potential to make more power with just valves and a head job but the potential of a stock internal 1NZ engine with just head work has yet to be realized. Many head jobs (good ones) will bear the ideal combination of performance, reliability, and drivability. This is done by balancing all of the head elements such as matching valve size and shape to seat geometry to port configuration. Bottom line: a head alone on many cars can conservatively net horsepower gains of 5 – 10% (and occasionally even more) and this is stage 1 on stock internals. But you probably already know this. Of course we will also have to get into the electronics...

It's true headwork and larger valves can gain power everywhere. But unless the stock valves are too small for the airflow requirements of the engine adding larger valves will hurt bottom end performance.

Now, I suppose the only way to really know if the valves are too small is to spend time with the heads on a flowbench and the car on a dyno.