Any of the Type IV heads can have valves the size of the 2.0 914's installed. I think they can all have larger valves installed, even--but it requires more and more work the larger you go, and too large can mess things up as well.

I think I've seen Raby state that the stock 2.0 ones are about as big as you want to go on a stock-ish 2.0 motor. But I could be misremembering....

--DD

GA and GC
 

I have a GA and a GC, both 2.0's. The GC case does not have an oil pressure control valve, whereas the GA does. Now some want to tell me that the lack of a control valve (not the pressure relief valve located on the bottom) is a bus motor. And others say that no valve means hydraulic lifters. I have strong reason to belive that both statements are false. First of all, the oil fill on the GC case is in the 914 position; secondly, this motor is a virgin and it has the real deal 2.0 heads complete w/ the EGR holes. So, I think Jake has it, case the same, oil system variations in later years.

On a smaller/stock 2.0 engine the 42x36 arrangement gives the best performance, as long as you have around 8-8.5:1 and a nice cam. When you get into more cam, and higher CR bigger valves work well.

I have noted that bigger valves make more power, no matter what, basically anytime, but the drivability goes to squat, especially down low unless you have the CR to pull out of it..

On a smaller/stock 2.0 engine the 42x36 arrangement gives the best performance, as long as you have around 8-8.5:1 and a nice cam.

Jake,

For the stock 2.0 engine with the above mentioned CR what would be your recommendations be for a "nice cam"? I have heard that the WebCam with the #73 grind is the cam of choice for this set-up, do you have something that works better?

My RAT 209 cam is based from the Web #73, it has different lobe centers, and seems to pull better that way...The 73 is a good cam!