other thant the fact that flat faced valves will raise compression. do they flow better in any way in a FI situation?

 

I am not an engineer or head porting specialist but with a mixture of past experience and some basic engine design theory, I would have to say the difference in flow would be nil. Like you stated, the flat faced valves will raise compression vs the dished ones. But as far as flow goes, that's really all in the port and valve job. The shapes and sizes of the backs on the intake and exhaust valves are what help dictate flow. The fronts (the parts that are either flat or dished) are just a ceiling to contain the combustion and really just get the air blown or sucked (lol, I know I'm immature) around them, so the small central difference won't net any substaintial gains in cfm flow. Anyone else who will back me up or has a differing theory, I would love to hear your 2 cents also.

 

i have the a theroy that flat faced valves at least on the exhaust side are benifical to exhaust flow. seing how as the shap "face" of the valves would allow the exhaust gasses to travel across the face much more efficiantly..

 

As I stated previously, there may be a slight advantage to flow on the exhaust side. The very nature of forced induction means it overcomes a number of flow related issues that would be a factor in an NA build. I would think for 95% of the FI builds on here, the slight differences between a flat faced vs dished face valve would be negligable.

The main purpose of flat faced valves is to increase compression slightly, that's it. They may also be of some benefit in a FI build as far as being able to handle a little more heat than a normal valve (because of extra mass) but honestly, the difference between a stock and flat faced valve would be splitting hairs.

 

the reason i ask is there is a build b16 head fs. but built for NA

 

Any idea how big the combustion chambers are on that head? In other words has it actually been cc'd? If it's in good shape and hasn't been planed a lot and priced right, you could use it on an FI build.

 

I have no opinion on the flow of the valves; however, the flat nature of the valve would be less prone to hot spots compared to the concave valves which could harbour hot carbon buildup and potentially cause detonation/pre-ignition. This may be a bit rare/extreme but could be a selling point if you plan to push this setup.