The best 4V cylinder heads are on the '00 Cobra R and Ford GT, but don't expect to find those cheap. The Mark VIII heads are good, though. They are known as the B heads, and you will be able to find lots of them for not a lot of cash. Incidentally, you can see why a four-valve-per-cylinder arrangement will always move more air than two valves. There's much more valve area. Antonette tells us about the best you can get out of a 2V engine is 500 hp, and you'll need forced induction to make that. Customers who want more than 500 hp are steered toward building 4V engines.