I dont remember seeing any 4 ohm heads. But, here's the deal... there's no need to go for the whole 'more is better' concept in
vaping. Yes, many people carry on about 'oh im
vaping at 6 volts!'... well ya, maybe with a 4ohm head...dont fall for that balogney. The voltage/ohms can be hard concept to grasp but high volts on a high ohm is the same as low volts on low ohm. It has to do more with how many watts are being put out.
IE
4.2 v with 2.4 ohm head = 7.35 watts
3.0 v with 1.2 ohm head = 7.5 watts (lower volts and lower ohm but slightly stronger vape)
Its one reason you see mods coming out with watt settings, because thats what is the real equalizer.
google 'ohms calculater' and play around with it. Most atomizers are good between 7-9 watts.
Personally, i build my stuff between 1 to 1.3 ohms and vape 3-3.6 volts.
(oh and above I meant 4.2v would be the most for a --- 2.4 --- ohm head)