A buddy of mine is interested in getting a 4v head and was wondering what the pros and cons are. His build atm is 61mm bbk 2.xx stroker big port head a12 camshaft uni and perf exaust.

You will have alot of power
The cost is high

Other than cost, the only other cons are that you have to replace the cam chain with a different length and the 4-head valves do not have a selection of cam grinds to choose from like the 2-valve.

The 4-valve head should give you a great performance boost and even better if you get it ported and polished. To see the difference in 4-valve verses 2-valve efficiency, compare the Chery 4-valve with the Suzuki 2-valve motors in the larger buggies.

Ok sounds fine to me. Do the shrouds have to be modified? I know the exhaust header will have to be right?

Yes to both but slightly.
The power you get is worth it

Btw
What buggy?

Crossfire 150. its got a hammerhead motor with aftermarket oilcooler plus the stuff listed earlier.

Sounds like Chucko old buggy

You might need a 4v piston too depending on the deck height

We was planning on getting a 4v piston anyway if we go this route

Wish there was a comparison of a 2 valve head, ported, with a choice of cam, and the 4 valve ported with the cam they provide to see the difference.

I still run the 2 valve head. my buggy is fast but the start off power is a little sluggish which is where the power gain is with the 4 valve head. I just haven't justified needing that low end power burst yet.