Just curious who does it? Also I have been told that their are some disadvantages of doing it. Can anyone explain?

 

Completely removing them will result in excessive wear of the valve seat because you lose that ability to hold the valve straight during high rpm usage. I have only known race only - short usage engines to completely remove the guide. I have seen it shaved down quite a bit though, which seems much more common as it is commonly the largest obstruction to air flow in the bowl.

 

Not sure of what heads you are talking about but if it is an LT1 head, the hole in the center of the guide is not "centered" to the guide and once reinstalled, the valve will be out of alignment and require some "work' to get all of the valves the same height. The added problems are probably not worth the minor gains from this.

It is possible to "crack" the heads from the guide boss into water jackets when re installing the guides. This will probably depend on how much metal was removed and what kinda "trama" the head sees during guide installation.

If you are asking for the LT1 heads, I would recommend against it.

I have never had these happen but I can definitely see that these things could happen.

NightTrain66