SO WHAT VE HEAD SHOULD I USE?
What head you should use comes down to availability, funding, and your power goals, as each of these heads has their own unique ups and downs. By far the cheapest head of them all is the P11 Primera head, or the Pulsar VZ-R head, which are identical apart from the camshafts. The Pulsar is more aggressive and better suited to naturally aspirated set-ups. Although the P11 head is by far the cheapest to buy from the get-go, it does need a lot more money spent for it to be suitable for a rear-wheel-drive conversion. A Primera P12 CAS has to be purchased, and extended ignition coils have to be used or external coils and leads, as the P11 still runs a distributor. One remedy for this is using the P12 rocker cover on the P11 head, which will allow you to run S15 or P12 coil packs, and these rocker covers can be sourced through Brendan at Pten Developments. A Nissan Primera/ VZ-R head will set you back around $400–$600 dollars depending on the condition and mileage, plus the cost of the P12 CAS, extended coil packs or external coils and leads, and a solenoid relocation kit.
By far the most superior head is the later-model Primera head from the P12. This head is named the 20V in enthusiast circles, and is by far the best total package. Firstly, there is no need to purchase the CAS as it comes installed from the factory. Secondly, it comes factory with the correct coil packs, which are identical to that of an SR20DET from the Nissan Silvia S15. Thirdly, the cams in the 20V head are the best of the lot, however, the exhaust cam isn’t as good as the SR20VET exhaust cam. Lastly, the 20V has one solenoid as opposed to the P11’s two, this is important because the P11 solenoids hit the firewall in a rear-wheel-drive application, whereas the 20V single solenoid clears the firewall with a bit of angle-grinder work. Another benefit of the 20V head is the injectors are top feed and, for example, Injector Dynamics ID1000cc are a direct fit without any modification, yet again saving you money as you don’t have to modify the fuel rail on the P11 head. The SR20VET head found in the Nissan X-Trail is identical to the P12 20V head, but it uses a different exhaust cam that is better suited for turbo applications. The exhaust cam doesn’t actually have VVL in the VET head, although both sets of cam lobes are present on the cam. By simply installing P11 or P12 rockers, this fantastic VET exhaust cam can be used.